Britain will do “everything it can to help” after reports of a series of explosions in Brussels, David Cameron has said.

Two blasts have rocked Brussels Zaventem international airport while another has been reported at a metro station in the Belgian capital.

The blast at the Maalbek metro station occurred in the close vicinity of the European Union institutions.

“I am shocked and concerned by the events in Brussels,” Mr Cameron posted on Twitter shortly after the news broke.

“We will do everything we can to help.”

People are evacuated from the Schuman station in Brussels (Evan Lamos/Twitter)

Mr Cameron himself has spent much time in Brussels recently, in and out of European Union summits to renegotiate Britain's membership of the bloc.

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The Belgian Government has said there have been a number of casualties in the explosions, but has not yet released any figures.

Belgium’s terror alert level is at the highest level following the arrest in the city of Salah Abdeslam, who authorities allege to have been centrally involved in the Paris terrorist attacks of November last year.