Suicide bombers who blew themselves up in Brussels were originally considering an attack on a nuclear site in Belgium, but arrests started last week may have forced them switch to targets in the Belgian capital, the DH newspaper said.

Referring to an incident in December that prosecutors confirmed in which militants covertly filmed the home of an unidentified senior official in the nuclear industry, the paper quoted a police source as saying that two of the suicide bombers, brothers Khalid and Ibrahim Bakraoui, had filmed the daily routine of the head of Belgium's nuclear research and development programme.

A 10-hour video from a camera hidden in front of the nuclear official's house was found in December during a police raid in Belgium, linked to the Paris attacks a month before.

On February 17, Belgian prosecutors confirmed the existence of the video seized in December and said the man in it was linked to the country's nuclear industry.

Earlier this month, 140 soldiers were dispatched to guard the country's three nuclear sites. On Tuesday after the Brussels bombings, the sites were sealed and non-essential staff evacuated as a precaution.