Greek authorities believe an extremist group may be behind a drive-by shooting outside the offices of the neo-Nazi Golden Dawn party in which two men were killed and another wounded, sources close to the investigation said Saturday.
Investigators are examining "all avenues, particularly those that link these events to extremist groups" behind a series of attacks on politicians, police, banks and the media, according to one source.
The revelation came as the mother of the wounded man, 29-year-old Alexandros Gerontas, called on Greek people to "overcome their differences" for the good of the country and to "stop the bloodshed".
In a television interview she described her son, who remains in hospital in a serious condition, as "peaceful" and said he visited the Golden Dawn offices occasionally but not regularly.
Her comments echoed appeals from Greek leaders and the media for calm in the wake of the shootings, which some fear could destabilise the already crisis-wracked country.
Greece's public order minister Nikos Dendias on Friday expressed his sadness at "the death of the young men", saying that "we will not allow our country to become a place to settle scores".
Centre-left newspapers Ethnos and Ta Nea described the shootings as an attack on "democracy itself", while the right-wing Eleftheros Typos said they targeted "the stability of the country".
Golden Dawn is Greece's third-most-popular party, with 18 seats in parliament.
Formerly on the fringe of Greek politics, the group boosted its popularity by tapping into widespread anger over immigration and austerity reforms in debt-wracked Greece, which is slogging through its sixth year of recession and where youth unemployment stands at 60 percent.
Friday's drive-by attack in Athens followed the killing in September of an anti-fascist musician, Pavlos Fyssas, by a self-confessed neo-Nazi.
The hip hop artist's death triggered public outrage, putting pressure on Greek authorities, who launched a crackdown on the party.
Attacks by groups describing themselves as revolutionary and anti-authoritarian are relatively common in Greece.
They are not usually fatal, although in 2009 a police officer was killed by three unknown gunmen in Athens and in 2010 a journalist was shot dead at his home. Both killings were claimed by the Sect of Revolutionaries, an extremist group.
Media reports said the weapon used in Friday's attack, by two unknown assailants on a motorbike, was the same type as the gun used in the 2009 shooting of a police officer.
The Sect of Revolutionaries has been quiet of late, but another extremist group called the Conspiracy of Fire Nuclei said in July it had entered into a "collaboration" with the group.
The Conspiracy of Fire Nuclei has claimed responsibility for a series of recent attacks including a bomb attack on the car of the Athens prison director.
The two men killed on Friday were Emmanuel Kapelonis and Giorgos Fountoulis, both in their 20s. A spokesman for Golden Dawn said they were members.
Police are hoping that footage from the security cameras of the Golden Dawn offices and shops on the same street will assist them with their investigation.