Police bomb disposal experts successfully defused a large homemade explosive device early yesterday which had been placed outside a bank in central Athens by an extremist group calling itself Revolutionary Brigades. Officers said the device contained a large gas cylinder and was put outside a branch of Emporiki Bank on the junction of Stadiou and Korai streets. The bomb disposal experts were called to the scene and sealed off the area after unidentified callers telephoned Mega and Antenna TV stations and the Eleftherotypia newspaper warning that the device would go off. Nobody was injured and no damage was done, police said. Revolutionary Brigades was also responsible for similar attacks this year, placing explosive devices near Korydallos prison last month and outside an army draft office in Rouf, central Athens, in May.