Dzhabrail Kostoyev, the deputy interior minister in the province of Ingushetia, died when a powerful car bomb exploded as drove past on his way to work near Nazran, officials said.
Two bodyguards and four bystanders were also reported killed.
A local interior ministry spokesman, Akhmed Aushev, and initial Russian media reports said the attack was carried out by a suicide bomber, but officials later said the car bomb may have been detonated by remote control.
"In all probability, there was no one inside the car that exploded," Dmitry Guruliyov, the deputy prosecutor for Ingushetia, said.
The explosion had a force equivalent to around 100 kilograms (220 pounds) of TNT, Mr Guruliyov said.
Police said a manhunt was under way in Ingushetia to catch the perpetrators of the attack.
The independent Russian radio station Echo Moscow suggested Chechen rebel warlord Shamil Basayev may have been directly involved in the planning of Wednesday's attack, which coincided with the murder of a prison official in another Russian Caucasus republic.
Attacks targeting Russian law enforcement officials are a frequent occurrence in Ingushetia, which borders Chechnya.
In June 2004, several hundred rebels led by Basayev launched a large-scale assault on Russian government installations in Nazran, leaving dozens of people dead, most of them police officers, and seizing an arsenal of weapons.
Since then, there has been a steady stream of attacks against Russian officials and security forces in Ingushetia, Dagestan and other provinces in the North Caucasus near Chechnya.
Clashes between rebels and Russian forces in Chechnya itself continue to claim lives on a near-daily basis.
Russian forces are also regularly shown on state television in
confrontations with "fighters" who usually number no more than two or three people holed up in an apartment building that is surrounded by special forces.