Ramzan Kadyrov – whose father is the pro-Moscow Chechen president Ahmad Kadyrov - told journalists on Sunday that gunmen had shot presidential security official Sultan Dadayev.
He blamed the "so-called Ichkerian armed forces" for sending assassins to storm Dadayev's house in the southeastern village of Allenroi and shooting him and his four bodyguards dead.
Kadyrov added that one of the attackers had also died in the shootout and four others were wounded, including the group's commander not far from Kadyrov's home town of Tsentoroi.
A Chechen law enforcement source quoted by the RIA-Novosti news agency said that Sultan Dadayev's son was also killed in the assault.
"The attackers, armed with automatic weapons, shot dead the security chief, his son and four members of his security force," the official said.
Kadyrov himself has been targeted in several assassination attempts by Chechen separatists, who brand him and other officials in the pro-Russian administration of the breakaway republic as traitors who must be executed.
Ahmad Kadyrov took office in
On Saturday, a police lieutenant was shot dead by unknown assailants in the war-shattered Chechen capital Grozny.
Russian troops poured into Chechnya in October 1999 in what the Kremlin described as an "anti-terrorist" operation, the second such war there in a decade.
The conflict has since degenerated into brutal guerrilla warfare, with troops, rebels and civilians killed nearly on a daily basis.
Some 5000 Russian soldiers have died, according to official figures. Although there are no official figures for Chechen casualties, some estimate that over 80,000 have died in the last ten years.
Russia refuses to hold peace talks with the rebels but insists that normality is returning to Chechnya after holding a much-criticised presidential poll last year that saw Moscow-appointed administrator Kadyrov elected as president.