PHOTOS: Explosions rock Brussels, terror attacks kill dozens

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Wednesday, March 23, 2016
Solidarity messages are written in chalk outside the stock exchange in Brussels on Tuesday, March 22, 2016.
A police officer directs passengers in a smoke filled terminal at Brussels Airport, in Brussels after explosions Tuesday, March 22, 2016.
The blown out windows of Zaventem airport are seen after a deadly attack in Brussels, Belgium, Tuesday, March 22, 2016.
In this photo provided by David Crunelle, an injured woman leaves the scene at Brussels airport, after explosions rocked the facility in Brussels, Belgium, Tuesday March 22, 2016.
A woman is evacuated in an ambulance by emergency services after a explosion in a main metro station in Brussels on Tuesday, March 22, 2016.
President Obama receives an update on the terror attacks in Brussels, Belgium. The President made the call from Havana, Cuba, March 22, 2016.
In this photo provided by Evan Lamos, passengers clamber from a metro carriage after explosions in Brussels Tuesday, March 22, 2016.
People walk away from the broken windows at Zaventem Airport in Brussels after an explosion on Tuesday, March 22, 2016.
A woman places candles in the shape of a heart outside the stock exchange in Brussels on Tuesday, March 22, 2016.
Two women wounded in Brussels Airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016.
A man is wounded in Brussels Airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016.
This photo shows the scene in Brussels Airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016.
''People wounded outside #maelbeek #metro #brussels''
''Metro Maelbee, fumee apres explosion.'' (''Maelbeek metro, smoke after explosion.'')
The scene in Brussels, Belgium following deadly explosions.
A young girl looks out of the window of a bus after being evacuated from the Brussels airport.
A police officer stands guard as people are evacuated from the Brussels airport.
People stand near the Brussels airport after being evacuated following explosions that rocked the facility in Brussels, Belgium, Tuesday.
People comfort each other after being evacuated from the Brussels airport.
A police officer, right, stands guard as people are evacuated near the Brussels airport.
People stand near the Brussels airport after being evacuated.
People react as they walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People react as they walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People react as they walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
People walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium, Tuesday, March 22, 2016.
A still from Associated Press video of the scene inside the Brussels Airport following explosions on Tuesday, March 22, 2016.
A still from Associated Press video of the scene inside the Brussels Airport following explosions on Tuesday, March 22, 2016.
A still from Associated Press video of the scene inside the Brussels Airport following explosions on Tuesday, March 22, 2016.
Smoke is seen at Brussels airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016.
A still from Associated Press video of the scene inside the Brussels Airport following explosions on Tuesday, March 22, 2016.
A still from Associated Press video of the scene inside the Brussels Airport following explosions on Tuesday, March 22, 2016.
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PHOTOS: Explosions rock Brussels, terror attacks kill dozensSolidarity messages are written in chalk outside the stock exchange in Brussels on Tuesday, March 22, 2016.
Geert Vanden Wijngaert/AP

BRUSSELS, Belgium -- Multiple explosions at two sites rocked the Brussels airport and the subway system Tuesday, killing at least 31 people and injuring at least 250.

An explosion on the rail tracks at the Maelbeek subway station near European Union offices killed at least 21 people, the city's mayor said in a news conference. Two more explosions at the departure hall of the city's Zaventem international airport killed at least 10, ABC News reports.

A suicide bomber appears to be responsible for at least one of the attacks, the Belgian federal prosecutor said. The city is now on its highest terror alert level.

Last Friday, Belgian police arrested the man suspected in the Paris terror attacks in November.

Raw video from the scene of the aftermath:

ABC News contributed to this report.

This is a developing story. Check back for updates.