The authorities in the north-eastern Indian state of Assam say paramilitary forces have killed at least three separatist rebels in an exchange of fire on Saturday.

Assam has a number of active guerrilla groups

Officials of the paramilitary Central Reserve Police Force (CRPF) say rebel fighters attacked a CRPF patrol in western Assam and both suffered casualties in the exchange of fire.

They say the rebels belonged to one of Assam's most powerful guerrilla groups, the outlawed National Democratic Front of Bodoland (NDFB).

The NDFB has been fighting state and central Indian authorities in their campaign demanding a separate homeland for Assam's Bodo tribesmen for the past 20 years.

The clash follows the arrest by Indian police of a senior NDFB leader a fortnight ago.

'Revenge' attack?

Officials say the rebels attacked a CRPF patrol in western Assam about 100 miles west of the state capital Dispur, and the soldiers returned fire.

The exchange of fire lasted almost an hour

The firefight is said to have lasted about 40 minutes in which three guerrillas were killed and several others wounded although officials say they managed to escape.

Two of the CRPF soldiers sustained serious wounds in the exchange of fire and are now being treated.

Correspondents say this is the first major clash between security forces and NDFB rebels since police arrested Govinda Basumatary, the group's General Secretary.

Peace talks

Mr Basumatary was detained while trying to board a train to Calcutta from where, intelligence officers say, he planned to fly to Bangkok.

Delhi says the NDFB operates from remote bases in southern Bhutan and is engaged in a rivalry with the other armed Bodo group, he Bodoland Liberation Tiger Force (BLTF).

In recent months, the BLTF has been holding peace talks with the Indian government, thus undermining the campaign for a Bodo homeland.

Indian officials say the NDFB is intensifying its violence ahead of a likely settlement between the BLFT and the government.