By Subir Bhaumik BBC correspondent in Agartala, north-east India

The Indian army is trying to take control of the Sajit Tampak area in Manipur's Kandu district, where three Manipuri separatist groups have bases. At least 19 rebels were killed in the last four days, army officials say.

But the Manipur People's Liberation Front told the BBC rebel fighters have beaten back a military offensive.

Heavy rains

A spokesman for the front, which is made up of three separatist groups in the state, said not less than 20 soldiers have died.

Last year, the Indian border security force failed to dislodge the rebels from Sajit Tampak and ended up suffering heavy casualties.

Both sides agreed that the recent fighting at Sajit Tampak had been heavy, despite incessant rains in the area.

The military offensive started early this week; a core commander of the Indian army, Lieutenant General Daljit Singh, is in Manipur to supervise the operation.

But local correspondents say that the army's efforts to take control of the remote hill region bordering Burma have been affected by bad weather which has made air support difficult to come by.

Last year, the rebels beat back a similar offensive by the border security force with heavy casualties.