Two Russian servicemen and two militants were killed in an overnight gun battle in the turbulent Northern Caucasus region of Chechnya, Interfax news agency reported on Thursday.
The four died during fighting at an apartment block in the town of Argun, just before midnight on Wednesday, the agency reported.
Five to six servicemen were injured, news agencies reported.
"For half an hour the separatists put up a fierce resistance to the Interior Ministry forces and police," Interfax quoted the federal military staff headquarters for the Northern Caucasus region as saying.
Chechnya, on Russia's southern border, is now relatively peaceful after two wars fought by separatist rebels and Islamist militants against Moscow's rule starting in 1994.
The region is run by Ramzan Kadyrov, a former rebel who declares loyalty to the Kremlin.
But the entire North Caucasus region, including Chechnya, continues to be the focus of clashes that have become more frequent in recent months.