Some 20 SU-24 and SU-25 fighter-bombers dropped bombs and carried out missile strikes in a wooded area where the rebels were hiding ahead of planned raids on the towns of Vedeno and Argun, a source in the Russian regional command told the military news agency.

The Chechen guerrillas suffered "severe losses," according to intercepted radio communications and aerial surveillance, the Russian official added.

The office of the Kremlin's top spokesman on Chechnya, Sergei Yastrzembsky, could not immediately confirm the information when contacted by AFP.

The Russian forces, who poured into the rebel republic in October 1999 and claim now to have largely pacified Chechnya, have not announced such large-scale operations for a long time.

Fighting also took place Wednesday on the border between Chechnya and the neighbouring Russian republic of Ingushetia between Russian troops and some 40 rebels, Ingush interior ministry officials told the RIA Novosti news agency.

The officials said that one federal soldier was wounded and five rebels died in the clashes, adding that the Chechen guerrillas managed to escape.

Meanwhile three Russian soldiers were killed and nine were injured Thursday when their bus drove over a landmine on a road separating two republics that border Chechnya, news agencies reported.

The bus was carrying a dozen interior ministry soldiers when it ran over the mine near a checkpoint on the border road separating Ingushetia from North Ossetia, ITAR-TASS quoted local police as saying.

The mine may have been remote-controlled, targeting the soldiers as they were returning to their base in Vladikavkaz, North Ossetia, it said.

Chechen separatist rebels have recently stepped up their attacks since a March constitutional referendum hailed by the Kremlin as signalling a normalisation of life in Chechnya.

WAR.WIRE