Greek authorities announced Saturday they had arrested three people and detained a further 15 in a "wide sweep" by the police's counterterrorism squad on suspected left-wing extremists that also yielded an arms cache.
Another person is at large, police announced Saturday, adding that the operation is ongoing.
Two of those arrested, and the one at large, all men in their 40s, face charges of engaging in terrorist action, illegal possession of firearms and explosives, and forgery. The three allegedly took part in a robbery on a betting shop in an Athens suburb on Oct. 21, police say.
The third arrested person, a 39-year-old woman was arrested for "violating the firearms law" police said.
The counterterror squad's sweep through 13 houses yielded, among other things, five AK-47 rifles, a submachine gun, two pistols, grenades, explosives and detonators.
Tests on the confiscated rifles showed that one AK-47 was used in the betting shop robbery and another was used in 2014, 2016 and twice in 2017.
In May 2014, on a European Parliament election day, shots had been fired at the offices of the socialist party, then ruling in coalition with the conservatives.
In January and November 2017, shots from the AK-47 were fired at riot police guarding the socialist party's offices. A police officer had been injured in the first of these attacks.
In July 2016, shots had been fired at the Mexican Embassy in Athens.
Also, in November 2016, a grenade thrown at the French Embassy, in central Athens, had injured a police officer.
All the above actions had been claimed, by a group called "Organization for Revolutionary Self-Defense" which had not operated before 2014.
One of the arrested men was jailed in 2010 for membership in the armed group "Revolutionary Struggle." He was released early in February 2018.