Explosions tore through the departure hall of Brussels airport on Tuesday morning killing at least 13 people and severely injuring 35 others and a second blast struck a metro station in the capital shortly afterwards, the Belgian public broadcaster RTBF said.

Francoise Ledune, a spokeswoman for the Brussels Metro, said on BFM television that there appeared to have been just one explosion, in a car that was stopped at Maelbeek.

The attacks came four days after the arrest in Brussels of a suspected participant in November militant attacks in Paris that killed 130 people. Belgian police had been on alert for any reprisal action.

The agency said shots were fired and there were shouts in Arabic shortly before the blasts at the airport.

Pictures on social media showed smoke rising from the terminal building through shattered windows and passengers running away down a slipway, some still carrying their bags.

Witnesses described the ceiling caving in and blood everywhere after the two explosions in the departure hall at the airport occurred at the middle of the busiest time there. Authorities told people in Brussels to stay where they were, bringing the city to a standstill. Security was also tightened at all Paris airports.

British Sky News television’s Alex Rossi, at the airport, said he heard two “very, very loud explosions”.

“I could feel the building move. There was also dust and smoke as well…I went towards where the explosion came from and there were people coming out looking very dazed and shocked.”

“The thinking here is that it is some kind of terrorist attack – that hasn’t been verified by any of the authorities here at the airport.”

RTBF said the metro station hit by the explosion was close to European Union institutions. Authorities closed all metro stations in Brussels, but there were no details immediately available of any casualties in this second incident of the day.

Belgian Prime Minister Charles Michel said on his twitter feed: “We are following the situation minute by minute. Our priority concern is for the victims and those present in the airport.”

Brussels airport said it had cancelled all flights and the complex had been evacuated and trains to the airport had been stopped. Passengers were taken to coaches from the terminal that would remove them to a secure area.

ISIS has claimed responsibility for the attacks in the Belgian capital on Tuesday, a news agency affiliated to the group said. The federal prosecutor said one of the explosions was probably triggered by a suicide bomber.

The coordinated assault triggered security alerts across Europe and drew global expressions of support.

European stocks fell after the explosions, particularly travel sector stocks including airlines and hotels, pulling the broader indices down from multi-week highs. Safe-haven assets, gold and government bonds rose in price.

French citizen Salah Abdeslam, the prime surviving suspect for November’s Paris attacks on a stadium, cafes and a concert hall, was captured by Belgian police after a shootout on Friday.

Belgium’s Interior Minister, Jan Jambon, said on Monday the country was on high alert for a revenge attack.

“We know that stopping one cell can … push others into action. We are aware of it in this case,” he told public radio.

French investigator Francois Molins told a news conference in Paris on Saturday that Abdeslam, a French citizen born and raised in Brussels, admitted to investigators he had wanted to blow himself up along with others at the Stade de France on the night of the attack claimed by ISIS; but he later backed out.