BOGOTA, Colombia (AP) _ A car bomb intended for the chief of the secret police killed his bodyguard and three passersby Tuesday, police said.

The chief of police, Gen. Miguel Maza Marquez, escaped with only bruises.

At least 37 others were injured in the assassination attempt that coincided with the start of a three-day international conference on how to protect officials from terrorism. Police said seven of those injured were bodyguards, and three of them were seriously hurt.

Maza Marquez, nicknamed ''Kojak'' because of his aggressive investigations of drug trafficking, was being driven to his office in a bullet-proof car when the bomb exploded in a parked car on a main street.

No one claimed responsibility, but suspicion fell on Colombia's powerful and violent cocaine trafficking cartels. They detest Maza Marquez, whose investigations have uncovered links between narcotics traffickers and the military and have led to many arrests.

Police said the blast killed one bodyguard traveling in another car and three passersby, including a policeman.

Also injured, mostly by flying glass, were about 30 passersby including two children who were waiting for a school bus.

Police said the bomb was planted in a stolen white Chevrolet Monza and apparently was detonated by remote control.

The blast reduced the car to twisted metal, damaged several buildings and shattered windows as far as three blocks away. The size or type of bomb were not known immediately.

Traffickers recently have targeted high-ranking justice and police officials.

Security and legal experts from the United States, Northern Ireland, Italy and France attended the conference, which was proposed by an international group in Washington that advocates more security and longer jail sentences for terrorists and drug traffickers.

It was the latest in a series of attacks in this nation plagued by drug traffickers, leftist guerrilla organizations and right-wing death squads.