French Interior Minister Gérald Darmanin on Friday warned of more attacks as the country was placed on maximum security alert following Thursday’s deadly attack by a knife-wielding man at the Basilica of Notre-Dame in the southern city of Nice.

“We are in a war against an enemy that is both inside and outside,” Darmanin told a French radio station. “We need to understand that there have been and there will be other events such as these terrible attacks.”