Unknown group claims Athens metro explosive device

An unknown group called the Urban Guerrillas claimed responsibility on Monday for an explosive device that was left on an empty Athens subway train over the weekend, but Greek police said the call could be a hoax.

"A man placed calls with two Greek TV stations, saying the device was the work of the Urban Guerrillas group and that other hits would follow," a police official said.

"There has been no such group in the past. It may be a credible threat or a hoax."

Greece's anti-terrorist force is investigating the incident.

A train driver found the device in a backpack on a seat on Saturday night.

The device, which was not activated, contained two small gas canisters with about 1.5 litres of gasoline, a timer, wires and batteries, police said on Sunday.

Fringe extremist groups have been frequently blamed for inciting violence during riots in central Athens against austerity measures imposed by the European Union and the IMF.

Small numbers of hooded protesters have regularly hurled petrol bombs at police during the demonstrations. Gas canisters have also been left at tax offices and politicians' offices.