Police have confirmed they have arrested a man suspected of discarding a package at the North Terminal of Gatwick airport.

Specialists have been called to the airport to investigate the item. The terminal has been evacuated, and some flights have been delayed.  

Detective Superintendent Nick May said: "At this time, we are investigating the circumstances of the incident and it is too early to say what the item may be. 

"However, given the events in Paris on Friday evening, there is heightened awareness around any such incident and it is best that we treat the matter in all seriousness. 

"We are aware that there is concern about what has happened in France, but the general threat level remains the same and people should be aware as usual of anyone acting suspiciously."

David Cameron has made a statement at Downing Street, saying the threat from the so-called Islamic State is "evolving", and becoming more acute.  

"We in the UK face the same threat," he said.

"We will redouble our efforts to wipe out this poisonous extremist ideology."

In the light of last night's attacks, the UK will review its terror plans and attempt to learn from what happened in Paris, he said.

Mr Cameron called the attacks the "worst act of violence in France since World War Two".

He said Britain stands with France "shocked but resolute, in sorrow but unbowed".

"While full picture is still emerging, we must be prepared for a number of British casualties, and we will do whatever we can to help those in need."

Long lines are forming outside hospitals as Parisians queue up to donate blood. Many are sharing pictures and information about which hospitals are most in need using the hashtag #dondusang, external.

The hashtag #porteouverte, external (open door) was also used throughout the night to offer rooms to anyone who needed somewhere to stay.

The Queen has sent a message to President Hollande, saying: "Prince Philip and I have been deeply shocked and saddened by the terrible loss of life in Paris. We send our most sincere condolences to you, the families of those who have died and the French people."    

David Cameron has warned that "we must be prepared for a number of British casualties" from the Paris attacks, as he condemned the "brutal and callous murderers".

Bavaria's state premier Horst Seehofer has said that there is "reason to believe" that a man arrested last week with several weapons in southern Germany is linked to the attacks in Paris. 

"There is reason to believe that this is possibly linked" to the attacks, Mr Seehofer told a party conference. 

Police made the arrest on 5 November during a routine check on a motorway and said they found "many machine guns, revolvers and explosives" in the suspect's vehicle.

A Syrian passport has been found on the body of one of the attackers, AP reports, citing police sources.

French TV is carrying the same line, but it has not been independently verified by the BBC.

Boris Johnson, the Mayor of London, has spoken about the attacks in Paris, which he called "our sister city".

"I have written this morning to Mayor Hidalgo to convey the sense of shock and grief of millions of Londoners at the tragic events in Paris. Our thoughts today are with the victims and their families and with the whole French people.

"We regard Paris as our sister city, a place for which we have deep reserves of love and admiration and respect. We are two capitals united in our values - democratic freedom, openness and tolerance. 

"The people who launched the attacks last night have no such values. They wish to undermine the things we hold most precious. They want to set neighbour against neighbour. They want to spread fear. 

"They will not succeed. As president Hollande has rightly said, they must and will be defeated. We stand ready in London to do everything in our power - to do whatever it takes - to assist in a struggle that embraces us all."

David Cameron, who is expected to make a statement shortly on the attacks, tweeted a message of solidarity to the French.

Ahmad al-Tayyib, the Grand Imam of Al-Azhar (one of the highest Sunni authorities in the Muslim world) has strongly condemned the attacks in Paris, state news agency Mena reports. 

Speaking during an international conference organized by the Ministry of Religious Endowments today, Al-Tayyib called the Paris terror attacks "chaotic", and stressed that Islam is innocent of terrorism. He also called for international cooperation to counter terrorism.

Israel will fly its flags at government offices and embassies abroad at half mast as a sign of solidarity with the French people, BBC Jerusalem producer Gidi Kleiman reports.

Israel's Prime Minister Benjamin Netanyahu has offered his condolences:

The claim was issued in written format in French and Arabic, and in audio format, all via established IS channels, according to the BBC's jihadist media expert Peter King. 

The statement claims that "eight brothers wearing explosive vests and assault rifles targeted carefully chosen locations in the heart of the French capital".

It goes on to call Paris the "capital of abomination and perversion".

"In a holy attack facilitated by Allah, a group of believers and soldiers of the caliphate – may Allah give it might and victory – targeted the capital of abomination and perversion, the one that carries the banner of the cross in Europe, Paris."

The Prince of Wales has condemned the Paris incidents as "bestial attacks" and said he wanted to express his "utter, total horror" at what had happened. 

The so-called Islamic State group has claimed responsibility for the attacks in Paris. 

In a statement published online, the jihadist group said the attacks were designed to show France it remained a "top target".

The group claims it studied the target locations and carried out the attack using "eight brothers wearing explosive belts and carrying assault rifles".

Russia is considering restricting flights from Moscow to Paris according to Russian news agency RIA, which cites Alexander Neradko, the head of Russian aviation regulator Rosaviatsiya.

Transport safety measures will also be implemented across the country following the Paris attacks, the agency reports.

Paris police have placed a temporary ban on demonstrations in the city and surrounding areas until Thursday.

Police are encouraging people who want to organise gatherings in private locations to postpone them, or to reinforce security.

Russian Foreign Minister Sergei Lavrov says international powers must do "much more" to fight Islamic State and groups like it, Reuters reports.

Ahead of a meeting with his US counterpart John Kerry and United Nations special envoy Steffan de Mistura, he told reporters:

A number of famous buildings around the world have bit lit up in the colours of France's Tricolour flag. Among them are Sydney Opera House, the CN Tower in Toronto and the spire of 1 World Trade Center in New York.

Red, white, and blue will be projected onto Tower Bridge in London on Saturday night.