BRUSSELS: Belgian federal parliament took additional security measures but kept its threat level at three on a four tier scale, a spokeswoman said, denying reports that the threat level for the institution had been officially raised.

"We have been told to take additional security measures, above ground as well as below ground," a spokeswoman said, adding the threat level for the building remained at three.

Belgium lowered the alert level for the whole country to three last week after a series of arrests of suspects following the March 22 bomb attacks in Brussels.