Belgium has raised its terror alert to its highest level and police have issued an arrest warrant for a man pictured pushing a laden luggage trolley at the airport, while two others are suspected of blowing themselves up.
At least 14 people died after two blasts tore through the departures hall of Brussels' main airport shortly just before 8 am local time.
Eyewitnesses have described the carnage which unfolded during the height of the rush hour.
"And then the second one came and that was really bad. The second one was like a fireball. I only saw, like a thick ball of fire, which was, like 20 metres from me.
"(translated)... I heard a gunshot and what sounded like Arabic, then I heard 'boom' - an enormous explosion. Afterwards people ran to the lift and others ran to the escalators. Two old people who came towards me - I saved them. I put them in the lift but they didn't want to let go of me."
A third bomb failed to detonate and was destroyed by authorities.
The blast at the Maelbeek train station, close to the European Union headquarters, occurred shortly afterwards, killing around 20 people and injuring over a hundred.
There's speculation that the attacks could to be linked to the arrest of French citizen Salah Abdesla, the prime surviving suspect for the November's Paris attacks who was captured by Belgian police after a shoot-out on Friday.
Raids have since been carried out with Belgian media reporting that police have found a bomb and an Islamic State flag during a house search in Brussels.
Prime Minister Malcolm Turnbull has tweeted that Australians are in solidarity with the people of Belgium following attacks causing multiple fatalities at Brussels airport and a metro station.
The Department of Foreign Affairs and Trade (DFAT) is urgently seeking to determine if any Australians were caught up in the violence.
Foreign Minister Julie Bishop says Australia's sympathies are with the people of Belgium.
"Our thoughts are with the people of Belgium and the government and the families of those who have been killed in these incidents. It proves yet again that no country is immune to terrorism. We are urgently seeking to ascertain whether any Australians were involved."
Opposition leader Bill Shorten says the attacks are a shocking crime.
"Many Australians have travelled to Brussels and any Australians travelling to Brussels will be shocked by the notion that the beautiful streets that they've walked in could be the scene for this evil terrorist activity."
