A Greek urban guerrilla group threatened on Wednesday to step up attacks and disrupt the tourist season in a pamphlet claiming responsibility for shooting dead a journalist last week.
Rebel Sect said it was behind the first killing of a reporter in the country in decades in a statement published in a the centre-left Ta Nea newspaper on Wednesday. Police said they believed the statement was authentic.
Sokratis Giolias, 37, who wrote for a popular news blog, was shot dead outside his home on July 19.
The group, which has also claimed the killing of a Greek anti-terrorism policeman in Athens last year, said it would target more policemen, journalists and prison staff.
"Tourists should know that Greece is no longer a safe haven of capitalism. We aim to transform it into a war zone of revolutionary processes, with arson, sabotage, fierce demonstrations, bomb attacks, armed killings," the group said in its statement. "We are at war with your democracy."
Rebel Sect, which emerged after the riots that paralysed Athens in December 2008, said it would not carry out indiscriminate killings and did not threaten to attack tourists.
Six people have died in attacks this year in Greece. A booby-trapped mail package went off at the citizen protection ministry in June, killing one of the minister's closest aides.
The increased guerrilla threat comes at a time of labour and social protests over austerity measures the government has imposed to tackle a severe debt crisis.
Labour unions have staged repeated strikes against budget and benefit cuts agreed with the International Monetary Fund and Greece's euro zone partners in return for a 110 billion euro ($138 billion) bailout package.