A powerful car-bomb set off by an apparent homicide attacker ripped through a convoy of vehicles in southern Russian on Wednesday, killing seven people including a high-level regional police official, authorities said.

Ingushetia's Deputy Interior Minister Dzhabrail Kostoyev, two of his bodyguards and four civilians were killed when a sedan packed with explosives blocked a road on the outskirts of the region's main city of Nazran and blew up, regional police officials and an Interior Ministry spokesman in southern Russia said.

According to preliminary information, a homicide attacker was in the car that exploded, ministry spokesman Roman Shchekotin said. However, Ingushetia's Security Council chief, Bashir Aushev, said it was also possible that the car bomb was detonated by remote control.

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Kostoyev, a target of previous attacks, had been traveling in an armored car to work in Nazran in a column of three cars, Shchekotin said.

Four civilians in at least one passing car were also killed, an official in the Ingush Interior Ministry said, speaking on condition of anonymity because he was not authorized to speak on the record. Russian media said they were innocent bystanders whose car slammed into stricken vehicles after the explosion.

Russian television networks showed footage of a gutted, blackened car on a road littered with debris.

Ingushetia, which neighbors Chechnya in Russia's restive North Caucasus, has been plagued by militant attacks, many targeting law enforcement officials and facilities. A concerted attack targeting police in Ingushetia in June 2004 killed 92 people.

Kostoyev, then Nazran's police chief, was wounded in August when unknown assailants detonated a radio-controlled land mine as his car was passing. The ITAR-Tass news agency reported that a mortar shell hit his office in a February 2005 attack, but that he was not there at the time, and RIA-Novosti said his home in the village of Ekazhevo was hit by gunfire twice late last year.

In another republic of the North Caucasus, Karachayevo-Cherkessiya, unidentified assailants fatally shot the acting chief of a prison in the city of Cherkessk early Wednesday outside his home.

Poverty, corruption and persecution connected with Islam have fueled anger at the authorities in the North Caucasus, an ethnically mixed strip of republics, most of which have large Muslim populations.

The region is troubled by violence in some cases linked to the conflict in neighboring Chechnya, where two wars have been fought in the past 12 years between federal forces and separatist Chechen rebels who haven increasingly espoused extremist Islamic ideology.