At least 20 people are feared dead and many wounded after a suspected suicide bombing and explosions at Brussels Airport and a Metro station in the Belgian capital.
Witnesses said the airport blasts happened shortly before 8am local time (7am GMT) in the departure hall near the check-in desks for American Airlines and Brussels Airlines.
Shortly afterwards, another explosion was reported at the Maalbeek (Maelbeek) station, near the European Council headquarters and other EU buildings. The capital's entire public transport system was being shut down.
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The Belga news agency reported that shots were fired before the explosions and shouting was heard in Arabic. But a witness, David Crunelle, said he did not hear "Islamic sentences".
Authorities have not released a statement confirming casualty figures but the VRT News quoted officials saying at least 13 had died and 35 were injured.
Police sources told VTM Nieuws 10 more people had been killed at Maalbeek Metro station but the toll has not been confirmed.
A Sky News journalist who was checking in at the time said he heard two very large explosions before being moved away from the area and that speculation of a terror attack was spreading.
An American couple, Andrew and Denise Brandt, said they felt the blast "like a wave" as they shopped on the other side of security barriers, before hundreds of people started running towards them.
Zach Mouzoun, who arrived on a flight from Geneva about 10 minutes before the first blast, told France's BFM television that the second explosion brought down ceilings and ruptured pipes, mixing water with blood from victims.
“It was atrocious," he said. “There was blood everywhere, injured people, bags everywhere. We were walking in the debris. It was a war zone.”
Footage showed passengers running from the terminal building as smoke poured through smashed windows.
The airport, which was exacuated, has been closed to all departures and arrivals as investigations continue. Rail services have been suspended.
The cause of the reported blasts has not been confirmed and police could not immediately be reached for a comment.
A spokesperson for Brussels Airport said: "There have been two explosions at the airport. Building is being evacuated. Don't come to the airport area.
"All airport operations have been suspended until further notice. Passengers that are still located in other area's in the airport are asked to remain calm and wait for further information."
The Belgian interior minister, Jan Jambon, said the national terror alert would be raised to its maximum level in the wake of the explosions, suggesting that authorities believe they were an attack.
Charles Michel, the Prime Minister, said the government was following the situation "minute by the minute" and that victims and bystanders were the priority.
A spokesperson for American Airlines said: “We are aware of an incident at the Brussels airport departure hall and are taking care of our customers, employees and contractors. At this time, all of our employees and contractors are accounted for with no reported injuries.
"American Airlines flight 751 (from Brussels to Philadelphia) has been cancelled for today. When operations at the airport resume, we will re-accommodate our customers."
Brussels has been under increased security measures since November's Paris attacks and has seen several operations in recent weeks linked to the hunt for Salah Abdeslam, who was caught on Friday.
Belgium's national crisis centre said all Metro stations, trains and public transport systems were being shut down in Brussels, urging residents to stay at home.
Meanwhile, EU institutions including those headquartered near Maalbeek station in Brussels were put on alert level orange, seeing meetings cancelled and access restricted and federal buildings were evacuated.
Martin Schulz, President of the European Parliament, wrote on Twitter: “My thoughts with Brussels and its citizens after these heinous attacks.”
Airports across Europe were increasing precautions this morning, including at Gatwick and Heathrow, which said there would be a "high visibility" police presence.
David Cameron said he would be chairing an emergency Cobra meeting with senior ministers and advisers later on Tuesday morning.
The Foreign Office is advising British citizens to follow the instructions of Belgian security services and to remain vigilant in crowded areas.
The official threat to the UK from international terrorism has stood at "severe" - indicating that an attack is “highly likely'' - since August 2014.
Are you in Brussels? Contact lizzie.dearden@independent.co.uk or call +44 0203 615 2419.
