BRUSSELS – An explosion was heard at Maelbeek metro station in Brussels, close to the EU institutions, Belgian broadcaster RTBF said, after explosions ripped through the departure hall at Brussels airport.

At least 13 people have been killed in the explosions at airport and subway station, according to Belgian media, with scores more injured.

The explosion at the metro station occured during the morning rush hour at about 8am at Maalbeek station. TV images showed black smoke billowing from the station entrance.

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Attaque à maalbeek. Trash

Posted by Adrien Sauvage on Tuesday, 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

Belgian authorities said metro, train and bus services in the capital Brussels have closed following the bomb blasts in the airport and metro, and have advised residents to 'stay where you are'.

Bus, tram and metro shut down," the Brussels public transport operator STIB said in a message on Twitter. Major railway stations are also closed, the Brussels public prosecutor said separately.

The city is in lockdown with the metro, bus and tram networks The metro operator later said on Twitter that metro service was being closed down.

The explosions that tore through the departure hall at Brussels airport on Tuesday (March 22) accounted for up to 10 fatalities, and 30 wounded. Belgian authorities have raised the terror alert to the maximum.