A time bomb exploded at the offices of JP Morgan brokerage firm in the central Athens district of Kolonaki around 7:50 p.m. local time on Tuesday evening, causing damages to the building, but no injuries, according to the first information by Greek police authorities.

Policemen seal off the area of the bomb explosion which occured outside the office of JP Morgan brokerage firm in Kolonaki district in central Athens, capital of Greece, on Feb. 16, 2010. The blast, causing damages to the building and no injuries, occurred 30 minutes after an unidentified man made a warning phone call to a Greek daily newspaper so that police had time to evacuate the building and seal off the crowded area. [Xinhua]

The blast occurred 30 minutes after an unidentified man made a warning phone call to a Greek daily newspaper, so police had time to evacuate the building and seal off the crowded area.

No group has claimed responsibility for the attack yet, but it is a common practice for Greek extreme Left and anarchist guerrilla groups to give warnings a few minutes before terrorist attacks.

Foreign economic targets, along Greek politicians and policemen, are the main targets of attacks of terrorist groups operating in Greece for years. Terrorist attacks have been stepped up in the country since December 2008, when a teenager was shot dead by police fire and Greece witnessed the worst riots in its recent history.

In the worst incident of the past year a policeman was fatally shot last June.

A few hours before Tuesday's bomb explosion, police exchanged fires with two bank robbers in Vyronas central district, leading to the death of one civilian and injuries to two policemen. The suspects, both Albanian nationals, were finally arrested.

Policemen seal off the area of the bomb explosion which occured outside the office of JP Morgan brokerage firm in Kolonaki district in central Athens, capital of Greece, on Feb. 16, 2010.[Xinhua]

Policemen seal off the area of the bomb explosion which occured outside the office of JP Morgan brokerage firm in Kolonaki district in central Athens, capital of Greece, on Feb. 16, 2010.[Xinhua]