Federal police issue a photograph of a man wanted over today’s bomb attacks in the Belgian capital, which killed dozens of people.
More than 30 people are believed to have died and more than 100 were wounded when bombs went off in the city’s airport, followed by a blast at a metro station.
Hundreds of passengers were trying to check in at Zaventem airport at around 8am when two explosions went off in the departure hall.
Another explosion struck the Maelbeek station in the city, close to EU buildings. Pictures appeared to show the aftermath of a bomb detonating on a train carriage at the station.
Belgian federal police released a CCTV still of a man suspected of involvement.
The suspect was dressed in a white shirt and jacket and wearing a dark hat, and was pictured along with two other men as they pushed luggage trolleys through the airport.
Prosecutor Eric van der Sypt said two bombers had died at Brussels airport and a third is being “actively” sought.
Belgian broadcasters RTL and RTBF reported that anti-terrorist police were carrying out searches in the Brussels districts of Schaerbeek and Jette.
The attacks came just days after the arrest of Salah Abdeslam, a Belgian man wanted over the deadly Paris attacks in November
The so-called Islamic State (IS) issued a statement claiming it had organised the attacks in revenge for Belgium joining the coalition that has been targeting its forces with airstrikes in Iraq and Syria.
The statement said: “A small group of Caliphate soldiers targeted the crusader country of Belgium which has been fighting Islam and its own people.
It went on: “A couple of caliphate soldiers equipped with suicide belts and carrying bombs and machine guns targeted very well chosen positions in Brussels, the capital of Belgium.
“They carried out their attacks inside Brussels airport and metro station, killing a number of the crusaders, before they martyred themselves by blowing up their suicide belts.”
Local news agency Belga also reported that shots were fired and there were shouts in Arabic shortly before the twin blasts ripped through the airport.
A federal prosecutor said the airport attack was the work of a suicide bomber.
The public broadcaster VRT later reported that police had found a Kalashnikov assault rifle next to the body of a dead attacker.
Terrified travellers were filmed running from the terminal as smoke poured from the building.
Other reports said the American Airlines desk in the departure hall was the site of the explosions.
Jef Versele, 40, from Ghent, said: “I was on my way to check in and two bombs went off – two explosions. I didn’t see anything. Everything was coming down. Glassware. It was chaos. It was unbelievable. It was the worst thing.”
He went on: “People were running away. There were lots of people on the ground. A lot of people are injured.”
Mr Versele said he was two or three floors above the explosion but many people near him were hurt.
“The bomb was coming from downstairs. It was going up through the roof. It was big. About 15 windows were just blown out from the entrance hall.”
Belgium’s prime minister, Charles Michel,said: “Ladies and gentlemen, what we feared has happened. Our country and our citizens have been hit by blind, violent and coward attacks.”
He added: “At this dark moment for our country, now more than ever I would like to appeal to all to be calm and show solidarity. We are confronted with a challenge, a difficult challenge and we must face it by standing united, showing solidarity and staying together.
We will continue to follow the situation minute by minute with the different security services, with the different emergency services.
“I would like to thank the security services for the work they are carrying out at this point and I would like once again to say we are determined to face, manage and follow this situation in the most appropriate manner possible.”
The attacks happened four days after the prime suspect in the Paris attacks, Salah Abdeslam, was arrested in the city.
Belgium has raised its terror threat level to four, the highest level. An extra 225 troops are being sent to the capital.
Security forces are carrying out house searches are ongoing in the region around Brussels.
The airport and whole metro system have been closed, and Eurostar said no trains would run to or from its station in Brussels.
David Cameron said the countries of Europe need to “stand together against these appalling terrorists and make sure they can never win”. He added that there was, as yet, no “hard information” about British casualties.
Downing Street later said one UK national had been injured, but there was no confirmation of any other British casualties.
Mr Cameron said he would chair a meeting of the Government’s emergency Cobra committee in response to the explosions in Brussels.
Police forces across the UK have increased their presence at key locations as a precaution, the country’s most senior counter-terrorism officer Mark Rowley has said.
Mr Rowley said: “The Metropolitan Police Service has mobilised additional officers who will carry out highly visible patrols at key locations around the capital, including the transport network.
“The number of officers deployed will be regularly assessed. These additional officers are deployed as part of reassurance measures. The police presence across London and the rest of the UK is constantly under review.
“We are in close liaison with the Belgium authorities and will continue to monitor the situation. The threat to the UK from international terrorism remains at severe as it has been since August 2014, meaning an attack is highly likely.”