BOGOTA, Colombia -- A car bomb exploded in central Bogota early Wednesday, killing six people and injuring at least 12, authorities said.

The explosion occurred in a commercial area filled with electronic, clothing and liquor stores as employees were arriving for work. The goods sold in the San Andresito neighborhood are contraband and much cheaper than those found in legal shopping districts.

Residents had alerted police to a suspicious Jeep in the neighborhood, police Gen. Jorge Daniel Castro told RCN Radio. When police went to check it out, the bomb exploded, killing two officers, he said.

Four civilians also were killed, and at least 12 were injured, Mayor Antanas Mockus told Caracol Radio.

Teodora Lagos, a cleaning woman, was entering a nearby bank when she heard the explosion.

"We all ran out, and looked around. There was smoke everywhere," she said. "I saw four dead people, including the woman who sells coffee here."

Lagos, 31, was outraged by the attack.

"This violence must stop!" she said. "Why must innocent people die?"

It was not immediately clear who was responsible for the attack.

Police have recently reported that right-wing paramilitary groups have been muscling their way in to San Andresito and extorting vendors there.

Leftist rebels fighting in Colombia's 39-year civil war have also increasingly been bringing the war to the nation's cities. In February, members of the Revolutionary Armed Forces of Colombia, or FARC, bombed an exclusive social club in the capital, killing 36 people and injuring 160 others.

The FARC was also blamed for an attack on a nightclub in the city of Florencia in late September that killed 12 people and injured dozens of others.

Colombia's long-simmering war pits the rebels against the government and the right-wing paramilitary fighters. About 3,500 people, mostly civilians, die in the war each year.