At least seven people were killed and 50 others injured Wednesday when a car bomb exploded in the port city of Buenaventura in southwestern Colombia.

Onlookers watch as a policeman stands near the scene of a car bomb in Buenaventura March 24, 2010. A car bomb exploded in the Colombian port town of Buenaventura on Wednesday, killing at least six people and wounding 50, the military said.[Xinhua/Reuters Photo]

The explosion occurred at 9:45 a.m. local time (1445 GMT) in downtown Buenaventura, just 20 meters away from the mayor's office, and caused huge damage to nearby buildings, police said.

The car bomb was detonated when a police vehicle passed by, immediately killing one policeman. The other victims included pedestrians and vendors.

Calling the terrorist attack "a massacre," Colombian Defense Minister Gabriel Silva said police had found some clues to the attack and offered a reward of 150,000 U.S. dollars for anyone who captured the terrorists.

Colombia's General Prosecutor Guillermo Mendoza said that "it gives an impression that it was a revenge against the Police and the Prosecutor's Office, but we cannot affirm anything."

Meanwhile, Commander of the Military Forces Freddy Padilla said it was a "terrorist" attack, which was related to the rebel Revolutionary Armed Forces of Colombia (FARC).