"Fourteen policemen died during the counter-terrorism operation in Grozny," Russian agencies quoted a ministry spokesman as saying of the violence on Thursday.

Previously Russia's National Anti-Terrorist Committee said that 10 police and 10 rebels were killed as heavily armed gunmen stormed buildings including a school and exchanged fire with security officers.

Twenty-eight policemen were injured, with 12 airlifted for emergency treatment in Moscow. The interior ministry gave no new details on the injured policemen on Friday.

Authorities declared the counter-terrorism operation over on Friday after closing off the city centre on Thursday and deploying armed personnel carriers. A local market, a high-rise building housing media and a school were heavily damaged by fire and shooting.

Moscow has battled a simmering insurgency for several years in the North Caucasus after fighting two wars against separatists in Chechnya, with the violence subsequently spreading throughout the predominantly Muslim region.

Thursday's raid followed a suicide blast in October which killed five policemen as they tried to stop the suicide bomber from targeting a packed concert hall.