An explosive device went off across from Greece’s labor ministry in the early morning hours of Saturday in downtown Athens.

The device exploded on the sidewalk of a main avenue following a telephone call warning of the bomb, made to an Athens daily (Efimerida ton Syntakton) just before 1 a.m., with the explosion coming roughly 40 minutes later.

No injuries were reported, only material damages, as the immediate area had been sealed off by police. The main street, Stadiou Avenue, remained cordoned off after dawn, with a bomb disposal unit collecting evidence.

The anonymous caller claimed responsibility on behalf of a group calling itself “Revolutionary Class Self-Defense”, possibly another name or offshoot of any of a handful of self-styled anarchist and anti-state urban terror groups that have plagued central Athens for decades. Initial assessments hold that the ministry was the target.

Police are scrutinizing footage from CCTV cameras.

In a later comment on Greek television, government spokesperson Pavlos Marinakis referred to a serious criminal act.