Two suicide bombers who blew themselves up in Brussels are believed to be brothers who were being sought for links with Salah Abdeslam, the prime suspect in the Paris attacks, RTBF television reported Wednesday, citing police sources.

Belgium pressed a huge manhunt after the Islamic State group bombers attacked Brussels Airport and a metro train, killing around 35 people and wounding hundreds as jihadists once again struck at the heart of Europe.

RTBF named the two as Khalid and Ibrahim El Bakraoui, saying Khalid last week rented an apartment in Brussels, under a false name, where police found Abdeslam’s fingerprints after a raid.

Police arrested Abdeslam, Europe’s most wanted man, in a dramatic operation in Brussels on Friday that had been hailed as a “victory” in Belgium’s campaign against terrorism.

Khalid is also linked to renting an apartment in the southern Belgian city of Charleroi from where Abdeslam and the other Brussels-based Islamic State jihadists set off to carry out the Nov. 13 Paris attacks which left 130 people dead.

A police source told AFP on Tuesday that a man in the middle of three men seen on closed circuit television at the airport just before the twin blasts could be Ibrahim El Bakraoui.

Other reports Wednesday said one of the brothers, who they did not name, could have been involved in the separate attack Tuesday on the Brussels metro station of Maalbeek, which left about 20 dead.

Belgian police earlier Wednesday issued an appeal for information about the two men believed to have blown themselves up at the airport.

The police posted several tweets with the caption “Terrorism: who knows this man?” showing CCTV close-ups of two men pushing trolleys with suitcases through the airport departure hall.

They gave three slightly different images for each of the two men who the federal prosecutor said Tuesday had likely blown themselves up in the attack.

A third man, dressed in a light-colored jacket and wearing a dark hat, who was shown with the two others in a CCTV grab issued Tuesday, is believed to have fled the scene and is now the subject of a massive manhunt.

Brussels residents held a candlelit vigil in the Place de la Bourse square where they sang songs and waved the Belgian flag, while on social media thousands of people shared images of beloved Belgian cartoon character Tintin in tears.

“This is a day of tragedy, a black day,” Belgian Prime Minister Charles Michel said, describing the bombings as the “deadliest attacks we have ever seen in Belgium.”

But as the nation began three days of national mourning on Wednesday, he insisted Belgium would not be cowed by the “blind, violent and cowardly” attacks.

“People were just going to work, to school and they have been cut down by the most extreme barbarity,” Michel said. “We will continue to protect liberty, our way of life.”

The Islamic State group claimed the bombings, saying “soldiers of the caliphate” had carried out the attacks against “the crusader state” of Belgium.

Leaders across Europe reacted with outrage, with the EU vowing to combat terrorism “with all means necessary” on a continent that has been on high alert for months.

“The whole of Europe has been hit,” said French President Francois Hollande, whose country is still reeling from November’s attacks.

Landmarks around the world, from New York’s One World Trade Center to the Eiffel Tower in Paris were lit up in the black, yellow and red of Belgium’s national flag in solidarity.

U.S. President Barack Obama vowed to stand with Belgium in the face of the “outrageous” attacks and ordered U.S. flags flown at half-mast, while the FBI and New York police said they would send investigators to help.

U.N. chief Ban Ki-moon said those responsible for the “despicable” bombings should face justice, while Belgian King Philippe condemned the “cowardly and odious” assault.

Hundreds of flights and trains were canceled as Europe tightened security, while across the Atlantic, New York and Washington ordered extra precautions at key areas.

There were chaotic scenes at Brussels airport after the bombers struck around at around 8 a.m., sending passengers fleeing in panic as plumes of dark smoke could be seen rising from holes punched through the roof of the building by the blasts.

“A man shouted a few words in Arabic and then I heard a huge blast,” airport baggage security officer Alphonse Lyoura told AFP, his hands bloodied.

“A lot of people lost limbs. One man had lost both legs and there was a policeman with a totally mangled leg.”

About an hour after the airport blasts, a third explosion rocked Maalbeek metro station, in the heart of the city’s EU quarter, just as commuters were making their way to work.

Paramedics tended to commuters with bloodied faces as the city’s normally peaceful streets were filled with the wailing of sirens.

Pierre Meys, spokesman for the Brussels fire brigade, told AFP at least 14 people had been killed at the airport, while Brussels Mayor Yvan Mayeur said “around 20” died in the metro.

More than 200 people were wounded in the two attacks, including four Mormon missionaries -- three Americans and one French -- two Britons and two Colombians. Eight French were wounded, the Foreign Ministry said, though it was unclear if this included the Mormon.

Belgian authorities published surveillance images showing the three male suspects of the airport attack. Two had dark hair and were wearing a glove on only one hand, and a third, who is being hunted by Belgian police, was wearing a hat and a white coat.

“They came in a taxi with their suitcases, their bombs were in their bags,” Zaventem Mayor Francis Vermeiren said.

“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 didn’t explode.”

Belgian authorities had been on alert after Abdeslam, Europe’s most wanted man, told investigators he had been planning an attack on Brussels. (AFP)