Two sex shops were hit by incendiary devices in the northern Greek city of Thessaloniki, causing some damage but no injuries, a police official said Tuesday.

The small gas canisters, which went off at the entrance of the shops Friday and Tuesday, are similar to the devices used by anti-authority movements that usually target government and financial facilities, police said.

Police believe the shadowy groups were responsible for these latest attacks and have ruled out any score-settling in the sex shop industry.

Left-wing extremists have stepped up attacks on government and financial targets since riots last December that were triggered by the fatal shooting of a 15-year-old boy.