Chechen separatists have killed seven Russian police in an ambush in southern Chechnya, one of the biggest attacks on federal forces this year.
Tuesday's attack was on a convoy near the village of Tai in Shatoi in the south of the territory, Russian news agencies said on Wednesday.
The convoy was returning to base when it was attacked.
Nikolai Varavin, a spokesman for Russian police in Chechnya, said: "The ambush occurred on a difficult, winding piece of road in a mountainous area, giving the attackers the advantage.
"It was an unexpected and well-planned attack.
"This was one of the most serious attacks on Russian police this year."
In July, an ambush killed at least six Russian soldiers and injured about 20.
Violence in Chechnya has been decreasing in recent years since Russia defeated several armed Chechen groups while negotiating deals with others.
Russian forces have pushed Chechen fighters deep into the mountains, driving them to resort to sporadic hit and run tactics.
Chechen leader Ramzan Kadyrov has made deals with rebels
Although tens of thousands of Russian troops are still based in Chechnya, analysts attribute the growing calm to Ramzan Kadyrov, the 30-year-old prime minister of the Russian-installed government of Chechnya.
Kadyrov is the son of a former rebel religious leader who had earlier defected to the Russian side and was assassinated in 2004.
Kadyrov and his father between them are estimated to have brought up to 7,000 rebels over to the Russian side - the biggest single step towards ending resistance in a decade.
Yulia Latynina, a commentator and Chechnya specialist, speaking to Reuters said: "Russians don't control this territory. The territory is controlled by those who fought [against Russia]."
Heavy civilian casualties
Since Chechen leaders unilaterally declared independence in 1991, more than 10,000 Russian soldiers are believed to have been killed in fighting in Chechnya.
During the same period, more than 100,000 Chechens are believed to have died, out of a total population of about one million.
More than 100,000 Chechens have also fled to other parts of Russia to escape the fighting.