ATHENS (Reuters) - A Greek urban guerrilla group claimed responsibility on Tuesday for a blast last month outside one of Greece's biggest TV stations and it accused media of promoting a "capitalist" agenda in the country.

In the claim posted on a website, the Group of People's Fighters (OLA), accused media of helping to preserve a "rotting economic and political system".

Greek authorities had considered the group a suspect in the Dec. 17 attack on Skai TV's headquarters in Athens.

The makeshift explosive caused widespread damage to the building in the early morning attack. Two warning calls had preceded the blast and there were no injuries.

OLA said the explosives had been placed in a manner to minimise the risk of injury, but added that the media were fair game to be on the receiving end of "social counter-violence".

"From the time of their creation private media businesses have been an incubator for the reproduction of a dominant far right, xenophobic and neo-liberal narrative, and as such are rightly the recipients of social counter-violence," the declaration said.

The attack on Skai was roundly condemned across the political spectrum as an attack on democracy.

Small-scale attacks on businesses, police and politicians are not uncommon in Greece, which has a long history of political violence and emerged in August from its third international bailout since 2010.

OLA emerged during Greece's debt crisis which broke out in late 2009. It claimed responsibility for two attacks in 2013 - on the headquarters of the conservative New Democracy party and on the German ambassador's residence, where more than 60 gun shells were found by police on the ground.

The group has also said it was behind a gun attack against the Israeli embassy in Athens in 2014 and a blast outside the premises of the Greek business federation in 2015.

It has also attacked banks and businesses in Athens.

(Reporting By Michele Kambas; Editing by Gareth Jones)