A blast has been hear at a metro station close to EU institutions in Brussels, shortly after loud explosions at the Brussels airport of Zaventem.

Police officials' estimates suggest at least one person has been killed. Belgian broadcasters RTBF and VRT say up to 13 people might have lost their lives and another 30 or more might have been wounded, while other suggest the number could be higher. Hospital sources say the death toll is at least 10.

People are still being evacuated at the airport as of 11:40 local time. Belgium's PM Charles Michel has urged the public to avoid "any movement". The EU has asked its staff to stay at their homes.

A two-kilometer cordon has been put in place around the airport.

Passengers still not evacuated have been moved to a parking area.

Zaventem international airport will remain closed until 06:00 local time, authorities say. The Netherlands has also raised security levels at airports.

EU Council meetings scheduled for Tuesday have been cancelled. The EU Parliament has not been evacuated, but has raised alert level.

All EU institutions are at alert level ORANGE - all meetings on premises and outside cancelled, access only for staff with badges

— Kristalina Georgieva (@KGeorgievaEU) March 22, 2016

Belgian authorities have a raised terror alert to the highest level. According to a local TV station, which doesn't cite its sources, the development was a suicide attack.

Belgium is sending an additional 225 troops to Brussels after the attacks.

Neighboring France has said it is deploying some 1600 extra security forces at the border and at transport hubs.

One of the blasts reportedly occurred next to the check-in counter of American Air, and the other next to a Brussels Airline counter. Shots were also heard before the explosions. 

Footage with people rushing out of the airport in panic appeared on social media seconds after the blasts were reported.

Pictures of the damages done on airport halls also circulated.

#BREAKING: Bombs detonated next to American Airlines desk at Zaventem airport in Brussels: 10+ injured pic.twitter.com/ykDpsc6hgV

— Amichai Stein (@AmichaiStein1) March 22, 2016

PHOTO: Damage inside #Brussels airport main terminal after two large explosions - @wardmarkey pic.twitter.com/n0Zjo33A6m

— Conflict News (@Conflicts) March 22, 2016

Over an hour after news spread of the two explosions, another one was reported at a the Maelbeek metro station, which is located close to EU institutions. 

All metro stations were closed down immediately and - subsequently - all public transport. AP reported smoke could be seen rising from a location near the EU Commission headquarters. The closedown of the metro and railway system later extended to other institutions such as museums.

No trains are running to or from Brussels to London or Paris as of the moment, Eurostar, which runs the high-speet links between the three cities. 

#Brussels metro in lockdown after explosion at #Maelbeek station - unconfirmed reports of attacks at other stations pic.twitter.com/RIiiRxGMFa

— James Holland (@James7Holland) March 22, 2016

Some local media say similar blasts have occurred at other stations as well.

The developments follow the capture in Brussels of Salah Abdeslam, one of the suspects for the Paris attacks in November.

Belgium's Interior Minister Jan Jambon had said authorities expected possible terror attacks in the days around the special operation.