Experts are worried about the resurgent of left-wing terrorism after an extremist organization claimed responsibility for the shooting of a Greek policeman. Can it be that an old problem in resurfacing in Europe?
The riots have pitted left-wing youths against the police
The fears were sparked after an anonymous caller to a Greek radio station said that the far-left group Revolutionary Struggle had been behind an attack on Monday, January 5 that left a Greek policeman in critical condition.
There was no immediate word on the authenticity of the caller, who said further attacks were imminent.
But authorities were talking the threat seriously.
The death of this teenager on Dec. 6 sparked the unrest
"This is a group clearly trying to murder police," Greek police chief Vassilis Tsiatouras, adding that Revolutionary Struggle had carried out other acts of violence in the past.
They included firing a rocket-propelled grenade at the US embassy in Athens in 2007. The US state Department has said it believes the group to have been behind nine such attacks since 2003.
"[The] attempted murder of three officers aims to undermine our country's democratic stability," Greek President Karolos Papoulias said in a statement.
New version of an old threat?
There have been solidarity demonstrations in Hamburg
Monday's attack comes after weeks of riots among left-wing youths angered by incident last December in which a Greek police officer shot to death a 15-year-old.
Now, some fear extremist groups could use the volatile mood in the country to help restart left-wing terrorism.
"There are extremists who are ready to use such violence -- not just firebombs but killings -- to keep the upheaval going," Costas Ifantis, professor of political science at Athens University, told Reuters news agency.
What some Greeks fear most is the revival of November 17 group, or N17, the left-wing, anti-capitalist organization that carried out dozens of assassinations and bombing attacks over three decades in Greece and only disbanded in 2002.
Europe's major left-wing terrorist organizations disbanded with the end of the Cold War
But one expert says there are differences.
"What you have are spontaneous, arbitrary attacks," former US diplomat in Athens, John Brady Kiesling told BBC news. "When there is a political window, they will mount an attack -- without the level of preparation that N17 used."
"They are dangerous, but not nearly as dangerous," Kiesling added.
Most Western European countries have been free of significant left-wing terrorism with the demise of groups like Germany's RAF and Italy's Red Brigades in the late 1980s and early '90s.
But the unrest in Greece has drawn expressions of solidarity from would-be revolutionaries in many parts of Europe, and an escalation of the conflict would raise at least the spectre of a resurgent form of left-wing terrorism on the continent.