The annual New Year's Eve festivities and fireworks in the heart of Brussels have been cancelled for security reasons, the mayor announced on Wednesday, as the Belgian capital remains on high alert over a possible terror threat.

"Unfortunately we have been forced to cancel the fireworks and all that was planned for tomorrow (Thursday) evening and that would have brought a lot of people together in the centre of Brussels, following a risk analysis by the crisis centre," mayor Yvan Mayeur told Belgian broadcaster RTBF.