ATHENS (REUTERS) - A small makeshift bomb exploded outside a Greek tax office in a wealthy Athens suburb on Thursday, damaging the entrance of the building and smashing windows but causing no injuries, police officials said.

Police had cordoned off the area in the upscale suburb of Kifissia, where many business executives and politicians live, after an unidentified person called a Greek newspaper and a news website around 0200 GMT warning a bomb would go off in 30 minutes.

No one has claimed responsibility for the explosion, which police officials said was small.

"The bomb contained a small amount of explosive material,"said a police official, who declined to be named.

Homemade bomb attacks by urban guerrilla groups are frequent in Greece, which is struggling to end its worst financial crisis in decades.

Attacks on political figures, police and justice officials have picked up in recent months, some claimed by anarchist guerrilla groups and anti-establishment leftists angry about Greece's financial woes.

In June, the anarchist guerrilla group Conspiracy of Fire Cells claimed responsibility for a time bomb that exploded outside the home of a prison director.