Shaid Bargishev reportedly lost both his legs in the explosion, but did not die instantly. Doctors started to operate on him, but he died later. Two of his bodyguards were also wounded in the blast.

The BBC's Damian Grammaticus: "Kidnapping has become commonplace in Chechnya"

The attack coincides with the start of a major security operation in the breakaway Russian republic against kidnapping gangs. Chechnya's beleaguered President, Aslan Maskhadov was quoted as saying the attack was meant to frighten law-enforcement officials.

Dozens of Russian soldiers and several foreigners, including three British and a New Zealand engineer, are still being held hostage, although several others have been freed in recent weeks.

'Releases to blame'

Mr Bargishev's death was confirmed by Supyan Akhmadov, head of the anti-kidnapping force's investigative department in Grozny.

BBC Moscow Correspondent Andrew Harding: "Chechnya's kidnapping gangs are fighting back"

Police said they were treating the explosion as a "terrorist act", but did not say if it was caused by an explosive device on the road or by a bomb placed in the car.

Husein Zabrailov, an investigator who worked with Bargishev in the anti-kidnapping department, blamed Sunday's bombing on the recent hostage releases. "The accident is a result of the work of the department," he said.

The kidnapped engineers - hostage taking has become a lucrative business

The BBC's correspondent in the region, Andrew Harding says that kidnapping has become a lucrative Business in Chechnya, with ransoms of as much as $1m changing hands.

The Chechen government has been struggling to impose order, but it has little money or authority.

Our correspondent says that the republic remains awash with guns and it is believed that powerful warlords may be involved in the kidnapping industry.