So-called Islamic State (IS) claims responsibility for Monday's truck attack at a Berlin market, which killed 12 people and injured 49
The registered driver of the Polish lorry is reported to have been found dead with gunshot wounds
German police have released a Pakistani suspect, saying there is no evidence against him
German Chancellor Angela Merkel and Berlin Mayor Michael Mueller attend a vigil at the Kaiser Wilhelm Memorial Church
Mr Mueller says "the entire free world mourns the victims of this cowardly and inhumane attack on our peaceful way of living"
Here are some more images of Mrs Merkel on her visit to the scene of Monday's attack.
The lorry has now been removed from the Christmas market, where passerby have been laying flowers.
Earlier, the German chancellor, who laid a white rose at the scene, said she was "shocked, shaken and deeply saddened'' by the apparent attack.
Image source, Reuters
Image source, ReutersChancellor Angela Merkel lays flowers at the site of the lorry attack in Berlin.
The prosecutors also say that they haven't yet finished the identification of the victims, but believe that most of them are German nationals.
They say that the authorities remain on high alert, trying to identify possible perpetrators.
BBC world affairs correspondent tweets...
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
Holger Munch, who heads Germany's criminal police office, tells the news conference that the authorities need to be prepared for possible copycat attacks.
The chief prosecutor says the fact the apparent attack was on a Christmas market was "symbolic" and it is impossible for such markets to be turned into "castles".
He tells the news conference that officials believe there is a terrorist background to the attack, but stresses that officials do not know whether there was one perpetrator, or several.
He says there has been no video from any group claiming responsibility for an attack, adding: "We can't yet really say anything definitely about the background."
Germany's chief prosecutor Peter Frank says the investigation is ongoing, adding that "we have to be open to the idea" that the detained man may not have been the attacker.
The prosecutor also says investigators are yet to establish whether the perpetrator or perpetrators had any support.
Image source, APNine people were killed in Munich in July
This is the fifth alleged terror attack in Germany this year.
The country last suffered a spate of violence in July, with four attacks in just a week.
On 18 July, a teenage Afghan refugee hacked at passengers on a train in Wuerzburg with an axe and knife, wounding five. He was shot dead by police.
On 22 July, a German teenager of Iranian heritage shot dead nine people in Munich before shooting himself dead.
On 24 July, a 21-year-old Syrian refugee killed a woman with a machete and wounded five other people as he fled before being arrested.
Later that day, a 27-year-old Syrian - whose refugee application had been refused - blew himself up outside a bar in Ansbach. Fifteen people were wounded.
Security services said the attacks were not linked, and there is some debate whether the 22 July shooting constitutes a terror attack, as police ruled out a political motive.
Read more here.
Berliners were out in the Christmas markets on Tuesday in a show of defiance in the face of terrorism.
Journalist Ann-Kathrin Hipp was sharing pictures of people who decided to head to Gendarmenmarkt, less than 3 miles (4.4km) from Breitscheidplatz.
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
These Berliners said they had make a conscious choice to go to the market but the attack was "always in the back of their minds".
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
These people decided to still come out because, they argued, an attack could take place at any time.
But their time in the market was cut short: Ms Hipp tweeted moments later that the market had announced that it was being shut early.
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
Many people in Berlin have been expressing shock at the lorry attack - including one young Muslim girl whose Facebook post is being widely shared.
Nemi El-Hassan says she has seen first-hand the effects of terrorism in Baghdad and Beirut and has always been thankful that she lived "on her secure island of Berlin".
Now that has changed she says:
Quote MessageAt the moment I can hardly believe what I'm seeing and at the same time I'm asking myself where I got this certainty from that we would always be spared terrorism here."
She describes how she felt when she heard the news, sitting in a restaurant:
Quote MessageI can't eat another bite, my stomach is heavy, my legs are shaking. All that is left to do is pray and hope for the wounded, the emergency services and those left behind."
Berlin's police president Klaus Kandt has told journalists he cannot confirm that the arrested man was the driver of the truck.
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
A quick round up of what we know so far about the Berlin lorry attack.
There's more detail about the events of last night here.
Germany's Die Welt, external newspaper is quoting a "high-raking security source" as saying the arrested Pakistani man is not believed to be the person who carried out the deadly attack.
The man has denied any involvement.
"The real attacker is still armed and on the loose and can do more damage," the source told the newspaper.
Police and special units have been informed, the source told Die Welt.
Berlin police have renewed their calls for people in the city to report anything suspicious:
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
Germany's Interior Minister Thomas de Maiziere has given a few more details about the arrested suspect.
He is from Pakistan, arrived in Germany on 31 December last year and came to Berlin in February. He then attempted to bring relatives over to Germany.
His asylum claim has not yet been decided upon. His name appeared in some official databases, but not in anti-terror ones.
Mr de Maiziere also said the pistol apparently used to kill the man found dead in the passenger seat of the truck passenger has not yet been found.
At the scene of the suspected attack, stallholders and well-wishers have been laying flowers and lighting candles in memory of those who have died and remain injured. Officials have said the Christmas market will remain closed for the rest of the day.
Image source, Reuters
Image source, EPA
Image source, Getty Images
Image source, AFP
Image source, AFP/GettyGermany has been left shocked by the apparent attack
Terrorism expert Anthony Glees has told the BBC that Mrs Merkel's decision to let in more than a million migrants last year has been "catastrophic" for Germany and the rest of Europe.
Quote MessageWe know that a large number of those people did not come from Syria at all and none of them were properly screened. If you simply open the borders you will include a very small number of highly dangerous people. You don't need many people to destabilise the rightful hold the government has on its people.
The migrants in Germany will in the future be able to travel freely through the Schengen passport-free zone, he says.
Quote MessageWhy are open borders meant to be European? It's nonsense, the European Union is essentially a state of nations build in a Judaeo-Christian setting. That's why Christmas markets are found everywhere, not just in Germany. So, Frau Merkel did not keep her people safe and she didn't keep us safe either.
Professor Glees says Germans must now overcome their aversion to surveillance by the security services and show that their democracy is a "muscular" democracy.
Quote MessageThe Germans are deeply, deeply suspicious, not just of interception as a security device but of their intelligence and security services. You can understand why if you're a history buff, you had Gestapo, the Nazi Third Reich, you had the Stasi, many Germans saying 'we don't want any of that'. But, of course, this isn't about yesterday it's about today and tomorrow.
Quote MessageThe only way you can stop these sorts of killers from operating is by knowing beforehand what their plans are and of course by protecting those very obvious signs. There's no more obvious sign than the site that the killer chose last night in Berlin, Germany's capital.
Quote MessageSo the Germans need to learn not only to get up to speed with interception and surveillance to give their community the sort of powers we give ours; also the French intelligence community now have and now use to their advantage.
Quote MessageIt's 70 years since the end of the Second World War, Germany has got to start showing that its democracy is a muscular democracy.
A journalist from the UK's Guardian newspaper has been speaking to someone who knew Naved B, the Pakistani man suspected of driving the lorry into the crowd of people.
The suspect has been arrested and is denying any involvement.
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
Image source, EVNGerman interior minister Thomas de Maiziere has been updating the situation.
He says there is "no doubt" that it was a terror attack.
In addition to the 12 dead, 48 people were hurt of whom 18 are “very seriously injured”, he said.
Among the dead is a man, who Mr de Maiziere says was found dead on the lorry’s passenger seat. He said the man’s injury had been caused by a pistol but investigations were continuing into when he was shot.
The man arrested after the attack has so far denied any involvement.
Mr de Maiziere said Germans must not let "our lives be determined by fear", otherwise the "enemies of freedom have already won".
Federal police in Germany are to hold a news conference at 14:30 local time (13:30 GMT) following the Berlin attack.
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
The Reuters news agency is reporting that the interior minister of the state of Saarland has said Germany is in a "state of war".
"We must say that we are in a state of war, although some people, who always only want to see good, do not want to see this," the minister, Klaus Bouillon, reportedly told German broadcaster SR.
