Organizers called off a march scheduled for Sunday in Brussels that was meant to show defiance of last week's bomb attacks, after senior officials urged people to stay away to avoid putting further strain on an overtaxed police force.

Belgium Saturday charged three people with terrorism in connection with the attacks at the airport and on a metro train Tuesday in which more than 30 people were killed and hundreds wounded.

In the following days, police carried out a series of raids and arrests across the city, and the government has maintained the security alert at Level 3, the second-highest level.

Brussels Mayor Yvan Mayeur and Interior Minister Jan Jambon asked for the demonstration to be delayed for several weeks.

"Given the security Level 3 and the capacity of the police, the interior minister and the mayor ask you to delay tomorrow's gathering," the mayor said on Twitter.

The organizer, Emmanuel Foulon, who is a spokesman at the European Parliament, said he fully understood that argument.

"The security of our citizens is an absolute priority," he said by email. "We totally agree with the authorities' request to delay this plan for a later date. We in turn ask citizens not to come to Brussels this Sunday."

The march, which organizers had expected thousands to attend, was meant to start at the Bourse (stock exchange), which has become a focal point for expressions of emotion for the victims of the attacks.