And that concludes our coverage for this evening, we will be resuming on Wednesday morning.

You can still follow the latest updates via the main news story.    

Image source, AFP

As a hunt for a suspect is under way, here are the latest developments from Belgium:

• Police are hunting for a man in a hat who was caught on CCTV pushing a laden luggage trolley at Zaventem airport before a twin attack there.
• An explosive device containing nails, chemical products and a flag of the so-called Islamic State were found during raids in Brussels.
• Police operations were still under way in the Schaerbeek area of Brussels well into the night.
• The threat level across Belgium has been raised to maximum, and troops have been deployed in Brussels.
• Security has also been beefed up in many other European cities.
• More than 30 people are believed to have been killed in the attacks.
• Here is our comprehensive round-up of all the day's events.
• Witnesses of the attacks share their experiences.
• And here are some of the most striking pictures of the day.

Katya Adler
Europe Editor

Image source, PA

You have that sense of anger and fear and sadness like you did in Paris after the attacks there. But what is missing here is a real absence of shock. 

This city has been in a state of public jumpiness and high security alert since those Paris attacks, and the massive manhunt here for key suspects linked to them.

In November, the city was in complete lockdown for days, no metro, all schools closed. But that is not to say there is a sense of inevitability about the bombings here.

There is a sense of public anger to a certain extent, a feeling that their government and the security services should have done more to keep them safe and should do more now, because the Belgian Prime Minister Charles Michel said there are more attacks to come.

So it is a case of when, not if.

UK Prime Minister David Cameron will chair a meeting of the government's Cobra emergency committee on Wednesday morning, Downing Street said.

The same group had a meeting on Tuesday to determine the UK's response to the Brussels attacks.

Image source, Getty Images

Image source, EPA

Belgian newspaper HLN reports the police were led to Schaerbeek by the taxi driver, external who dropped the suspected bombers off at the airport.  

He recalled that they would not let him help them with their luggage, and told police where he had picked them up from.

The BBC's Anna Holligan says while the helicopters have gone, there is still a lot of activity in the Brussels area.

Two cars carrying police in balaclavas, possibly special forces, have been seen as well as at least two Red Cross vehicles.

She says she has also seen unverified footage from a resident which appeared to show two people being arrested.

In the meantime, people are still waiting to return to their homes.

Image source, Reuters

Here is how some world leaders have reacted:

• US President Barack Obama: "We must be together regardless of nationality or race or faith in fighting against the scourge of terrorism... We can and we will defeat those who threaten the safety and security of people all around the world."
• UK Prime Minister David Cameron: "These are appalling and savage terrorist attacks... These were attacks in Belgium. They could just as well be attacks in Britain or in France or Germany, or elsewhere in Europe and we need to stand together against these appalling terrorists and make sure they can never win."
• German Chancellor Angela Merkel: "We will cooperate in every way with his government and with the Belgian security forces to find, arrest and punish those responsible for today's crimes... The horror is as limitless as the determination to overcome terrorism."
• UN Secretary General Ban ki Moon, through spokesman: "The despicable attacks today struck at the heart of Belgium and the centre of the European Union. The secretary-general hopes those responsible will be swiftly brought to justice. He is confident that Belgium's and Europe's commitment to human rights, democracy and peaceful coexistence will continue to be the true and lasting response to the hatred and violence of which they became a victim today."

Here are other pictures of the makeshift memorial which has popped up in the Place de la Bourse, Brussels.

You can see some other pictures of the day here.

Image source, AFP

Image source, AFP

Image source, AFP

Image source, AFP

Belgian Prime Minister Charles Michel joined crowds gathered at the Place de la Bourse in Brussels, where a makeshift memorial has popped up.

He is pictured here on the right embracing European Union Commission President Jean-Claude Juncker.

BBC Monitoring

The Brussels authorities have announced that a minute of silence for the victims of the attacks will be held at midday local time (11:00 GMT) on Wednesday, the website of the Belgian public broadcaster RTBF reports.

Image source, AP

Belgium's interior minister said authorities knew that some kind of extremist act was being prepared in Europe but they were surprised by the scale of the attacks in Brussels. 

Interior Minister Jan Jambon said: "It was always possible that more attacks could happen but we never could have imagined something of this scale". 

Officials at Denver International Airport have evacuated a section of its main terminal as they investigate a possible security threat.

Flights, though, have continued, they say.

Image source, AFP

Belgian Health Ministry tells the BBC there are approximately 30 dead and about 250 injured.

A spokeswoman said it was difficult to ascertain how many were wounded as some made their own way from the attacks at the metro station and airport.

She said the ministry was very happy with the emergency services' response, and they were well prepared as their capacity to deal with such situations had been evaluated in the wake of last year's Paris attacks.

When the first attack happened at the airport, Brussels' emergency services attended, while emergency services from neighbouring regions were put on standby and parked up outside city, she added.

The worst injured victims at Zaventem Airport were taken to the nearest hospital, and all others were taken to hospitals in neighbouring regions, taking into account possibility of a second attack.

When the second attack occurred at Maelbeek metro station, the reinforcements waiting outside Brussels attended as planned, she said.

Image source, AFP

The three suspected attackers who struck Zaventem airport had their bombs in their luggage, the local mayor told AFP news agency. 

"They came in a taxi with their suitcases, their bombs were in their bags," Zaventem mayor Francis Vermeiren was quoted as saying.

"They put their suitcases on trolleys, the first two bombs exploded. The third also put his on a trolley but he must have panicked, it did not explode."

In addition to France's Eiffel Tower, other countries have shown solidarity with Belgium by lighting up their buildings in the colours of the Belgian flag.

We have more pictures of the day's events here.

Image source, EPA

Image source, AFP

Image source, AFP

Brussels airport officials confirm that the city's airport will remain shut on Wednesday and could re-open on Thursday - but only after an expert evaluation. 

US European Command is prohibiting unofficial travel to Brussels for military personnel, and those on official travel will need approval. 

"We will assist Belgium in any way our military can - we strongly condemn these attacks and will continue to stand by our Nato allies and partners to defeat these terrorists who threaten our freedoms and our way of life," General Philip Breedlove, the Nato supreme allied commander and head of US European Command.

Earlier, US European Command said it was aware of one US service member and his family who were caught up in the attacks. No other details were given.

The BBC's Gavin Lee tweets from Brussels:

Head of US Homeland security Jeh Johnson said the US had no intelligence that indicated there was a plot to carry out an attack similar to the one in Brussels 

"At present, we have no specific, credible threat of any plot to conduct similar attacks here in the United States," Mr Johnson said in a statement. 

He added that security was being ramped up at major airports, and rail and transit stations.

Image source, Getty Images

President Barack Obama said the US-led coalition would continue "pounding" Islamic State targets in Iraq and Syria following the attacks in Brussels.

"We're going to go after them," the US president told ESPN during his visit to Cuba.

IS has claimed responsibility for the attacks in the Belgian capital.

Image source, Reuters