Belgian police sources have named two brothers as being involved in fatal explosions at an airport in Brussels on Tuesday, according to local media.

Khalid and Ibrahim El Bakraoui were named as the suicide bombers responsible for two separate blasts in the departure hall at Zaventem airport, which killed at least 14 people. They were reportedly known to police.

A third suspect, who was believed to have escaped the airport, was named by the federal prosecutor as Najim Laachraoui according to Belgian state media.

Previously known under the false name of Soufiane Kayal, he was the same man allegedly involved in bomb-making activities in the November Paris attacks.

At least 34 people died and 200 were injured in two explosions at Zaventern airport followed about 90 minutes later by a blast inside a rush-hour train in the underground Maalbeek Metro station. The attacks have been claimed by Islamic State (IS).

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On Wednesday morning (AEDT), Belgian police executed two raids on two separate properties in the Brussels district of Schaebeek, and reportedly located an IS flag, explosive device containing, among other things, nails, and chemical products.

“What we feared has happened,” Belgium’s Prime Minister Charles Michel said at a press conference. “I would like to tell you this time, this tragic moment, this black moment in our country, I would like to call on everybody to show calmness and solidarity.”

Mr Michel described the attacks as “blind, violent and cowardly” but insisted Belgium would not be cowed, as he announced three days of national mourning and raised the terror alert to the highest level possible.

IS claimed responsibility through the Amaq Agency, a smartphone app used by the terror group to issue statements: “We promise the crusader alliance against the Islamic State that they will have black days in return for their aggression against the Islamic State.”

Belgian police confirmed a photo of three men distributed widely by European media outlets was of the key suspects. All three pushed luggage trolleys in the photo.

Two men wore gloves on their left hands only; they were reportedly the El Bakraoui brothers who died in the blast.

A third man in a hat and glasses (pictured above) is thought to be at large. Belgian police issued a wanted notice for his arrest. It was reported that the suspects were carrying bombs in their bags.

Australian Prime Minister Malcolm Turnbull confirmed on Wednesday morning (AEDT) that there were no reports of Australians being injured so far and condemned the “cowardly” attacks.

Earlier, Mr Turnbull posted to Twitter: “Deeply concerned by the attacks in Brussels. Australians’ thoughts, prayers and solidarity are with the people of Belgium.”

The explosions happened four days after the Brussels arrest of a suspected participant in November’s IS attacks in Paris that killed 130 people. Belgian police had previously said they were on alert for any retaliatory action.

Travellers make their way through the smoke-filled Zaventern Airport. Photo: AP

The inside of the departure hall after the explosion. Photo: Twitter

Many survivors of both attacks reportedly suffered lower leg injuries and puncture wounds inflicted by nails and screws. This suggested the bombs were detonated at ground level and packed with shrapnel to cause maximum damage to the victims.

Airport worker Alphonse Youla, 40, described horrific injuries to people in Zaventern airport.

“The tiled ceiling of the airport collapsed. I helped carry out five dead, with their legs destroyed, as if the bomb came from a piece of luggage,” he told reporters, his hands covered in blood. “It’s from the people I carried out”.

All public transport in Brussels was shut down, as it was in London during the 2005 militant attacks on the underground that killed 52 there.

Commuters comfort victims outside Maalbeek station. Photo: Twitter

A victim receives first aid near Maalbeek metro station. Photo: Getty

Emergency vehicles gather in a street near the station. Photo: Getty

It is believed the airport explosions occurred next to the American Airlines check-in desk at 8am local time. The airport was evacuated and was closed to flights.

Video from the airport appeared to show people running from the building, as smoke billowed from the roof. Several windows were also smashed.

A witness said he heard shouts in Arabic shortly before the two blasts.

Sky News journalist Alex Rossi, reporting from 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.”

A man lies injured in Zaventern Airport. Photo: AP

Mr Youla said he heard a man shouting in Arabic before the first explosion.

“Then the glass ceiling of the airport collapsed,” he said.

Security services found and destroyed a third bomb at the airport, according to the provincial governor of Flemish Brabant.

People were forced to get off trains in Metro tunnels and walk to nearby stations. Trains between Paris and Brussels were later cancelled.

A security guard assists a woman wounded in the explosion at Maalbeek metro station. Photo: Getty

More than 500 troops have been deployed to the region to bolster security.

Other countries in the European Union also responded. France deployed an extra 1600 police at its borders after the explosions, while additional protection was sent to key locations in the United Kingdom.

We are too scared to go out: Aussies

An Australian who flew into Brussels Airport during the terrorist attack said passengers were left on board on the tarmac while the horror unfolded.

Leigh Dryden was on one of the last flights to land at Brussels airport shortly after two deadly bombs went off in the terminal.

“As the plane touched down we saw the first puff of smoke over the terminal. The plane came to a sudden stop,” he told ABC News Breakfast on Wednesday morning (AEDT).

Mr Dryden said within 15 minutes all those on board were made aware of the attacks, and sat on the plane for about 90 minutes before they were whisked away from the main terminal.

“It was chaos,” he said.”

Belgian police search for a suspect. Photo: Getty

Australian exchange student Mia Egerton-Warburton, who flew into Brussels on Monday night, said her group had been warned to stay indoors and that all public transport had been shut down.

“We’re feeling a bit shocked, confused and wary of possible further attacks,” the 20-year-old told AAP.

“To give you an insight into how tense it is, a car alarm just went off in the street outside our room and literally everyone was looking out their windows. People stopped walking.”

The University of Western Australia student, who has been studying in the UK, said her group’s plans for sightseeing had been cancelled and they would now leave Brussels on Wednesday.

“All our families are pretty panicked, basically telling us to get out of Belgium,” she said.

“We are too scared to go to the grocery store at the moment, so we are basically stuck inside hungry.”

A candlelight vigil was held at Place de la Bourse in central Brussels.

A soldier secures the perimeter in front of Grand Central Station in Brussels. Photo: Getty

‘Instantly, everybody started screaming’

Witness and Belgian David Crunelle, 36, who was at the airport to catch a flight to Japan, spoke to the ABC’s 7.30 program on Tuesday night (AEDT).

“I was putting my luggage at the drop-off,” Mr Krenell said.

“An explosion happened in the terminal for the US departures. I think it was American Airlines terminal. Two explosions, [with] like two or three seconds between the two explosions. Everything went dark.

“There was a lot of people injured. Instantly, everybody, they started screaming and crying a lot, exiting — the people from the airport and from the airline companies — everybody went out without knowing what to do but it went well.”

Mr Crunelle said the injured were driven to a separate building.

“I can only tell you what I saw and that’s 30 or 35 people slightly injured and about five or six people laid on the floor at the entrance waiting for the ambulance,” he said.

“I know that there are some damaged people. The police just said that there were dead people as well.”

Australians with concerns about family and friends should attempt to contact them directly, according to DFAT. If you are unable to reach them, contact DFAT’s 24 hour consular emergency centre on 1300 555 135.

See video from the airport below:

#BREAKING: Two loud explosions at #Zaventem airport in #Brussels pic.twitter.com/JFw9RGLjnh

— Anna Ahronheim (@AAhronheim) March 22, 2016

#Breaking: 2 explosions rock #Brussels airport. pic.twitter.com/SjPp8TeVoH

— Zaid Benjamin (@zaidbenjamin) March 22, 2016

This was the scene a short while ago, between the Arts-Lois and Maelbeek metro stations in Brussels. pic.twitter.com/aTZjqsF7Gt

— Evan Lamos (@evanlamos) March 22, 2016

– with reporting by Anthony Colangelo, Emma Manser, Jackson Stiles, Kaitlin Thals and agencies