A small bomb exploded in central Athens, outside the offices of a Greek construction company, police said early Saturday. No one was hurt in the time-bomb blast which occurred shortly before midnight Friday following a warning telephone call to a daily newspaper, police said. The device exploded outside offices of the J&P-Avax construction company, about 150 meters from the Greek Police headquarters. There was no immediate claim of responsibility for the blast, the third unclaimed attack in seven months, which has raised fears of a resurgence of far-left Greek militant groups.