Greek police say a gun fired against police outside a political party headquarters in Athens was used in past attacks claimed by domestic far-left extremists.
No group has claimed responsibility for Tuesday's attack outside the main office of the opposition Pan-Hellenic Socialist Movement. One policeman was injured.
A police statement Wednesday said tests on bullet casings and fragments from the scene matched an assault rifle used in attacks on the same party's offices in 2014 and on the Mexican embassy in 2016, AP reported.
These attacks, which injured no one, were claimed by the Organization for Revolutionary Self-Defense. The same group claimed a hand grenade attack last year that lightly injured a police guard outside the French embassy in Athens.