 A bomb exploded Sunday at a shopping mall in Athens, slightly wounding two security guards, police said.

Two warning phone calls were made to local media about 50 minutes before the blast, and authorities evacuated about 200 people from the mall, located in the Maroussi suburb north of the city center, a police official told the Associated Press. The official spoke on condition of anonymity because he was not authorized to speak to the media.

Shops are closed at the mall on Sundays, but cafeteria, restaurants and movie theaters in the complex, two levels above where the bomb exploded, are open. The device exploded about 20 minutes before some movies were scheduled to start showing, mainly children’s films.

The device was a small bomb that is believed to have been planted in a trash bin. The blast caused minor damage to stores, the official said.

The two wounded security guards were transported to a nearby hospital and were released an hour later, local TV stations reported.

There was no immediate claim of responsibility.

Small armed groups have been active in Greece for decades, usually planting small explosive devices late at night at bank ATM machines, car dealerships or foreign company offices. Attacks in public places during the daytime have been rare.

Police were examining whether the attack might have been carried out by the same group that carried out a shooting attack against the offices of the governing conservative party on Jan. 14. Shots were fired at the building from an assault rifle, causing no injuries. No group has claimed responsibility for that attack.