A series of raids have taken place across Brussels in connection with the attacks that left 34 people dead
A bomb containing nails has been found along with an Islamic State flag in police raids in Brussels, according to prosecutors.
The discovery was made during a search of an apartment hours after the Belgian terror attacks, which killed at least 34 people.
"The searches that took place in the Schaerbeek (district) found an explosive device containing among other things nails," the federal prosecutor said in a statement.
"Investigators also discovered chemicals and a flag of the Islamic State," the statement added.
A series of raids are taking place across Brussels in connection with two bomb blasts at Zaventem Airport and an explosion at Maalbeek metro station.
Belgian authorities have released a photograph showing three suspects caught on CCTV cameras at the airport.
Two men seen in the photograph wearing dark jumpers are believed to have blown themselves up in the terror strike, which began around 8am local time.
A third man wearing a hat is understood to have fled the airport.
Belgian authorities have issued a wanted notice for the man and anti-terror police are searching the districts of Schaerbeek and Jette.
Zaventem mayor Francis Vermeiren said the attackers arrived by taxi and the bombs were in their bags but the third suspect "must have panicked" as his device "didn't explode".
The two suspects in dark tops appeared to wear dark gloves on their left hands and security experts suggested the gloves could have been used to hide triggering devices for bombs.
Islamic State claimed responsibility for the bombings in a statement released online.
"We promise the crusader alliance against the Islamic State that they will have black days in return for their aggression against the Islamic State," the extremist group said.
The AMAQ news agency, which is affiliated to the jihadist organisation, added: "Islamic State fighters opened fire inside Zaventem Airport, before several of them detonated their explosive belts, as a martyrdom bomber detonated his explosive belt in the Maalbeek metro station."
At least 34 people were killed and nearly 200 wounded after the apparently co-ordinated attacks in the capital on Tuesday morning.
Shots were fired as the perpetrators at the airport reportedly shouted in Arabic before two explosions ripped through the departure hall.
At least one of the bombs was believed to have been hidden in a suitcase, according to security officials, adding there was concrete evidence of one suicide bombing.
The Belgian prime minister Charles Michel has declared three days of national mourning.
He joined crowds gathered at a square in the centre of Brussels to light a candle in memory of the many victims.
Newstalk.com's Shona Murray, who is in Brussels, said there was still a lot of activity in the city tonight, explaining "it is quite solemn and quite tense":
The attacks come a few days after Salah Abdeslam, a suspect in last November's Paris massacre carried out by IS, was arrested in the Molenbeek area of Brussels after four months on the run.
"It is too early to establish a link with the Paris attacks," said federal prosecutor Frederic Van Leeuw.
Since his capture last Friday, Abdeslam has been questioned by investigators and he told them he was planning new operations from Brussels.
Authorities said at the time they were taking the claim seriously because they had found "heavy weapons" and evidence of a network of people around him.
Prosecutors said two detonators and a large cache of weapons were found in an apartment from which Abdeslam was thought to have fled from last week before eventually being apprehended.
Belgian authorities fear he had accomplices while on the run who are still at large and could pose a threat.