The move came as Bhutan said its forces were "in hot pursuit" of the rebels.

More than 2,000 guerrillas were being pursued after Bhutan launched the offensive December 15 to expel the rebels from camps in the south of the tiny Himalayan kingdom from where they have staged hit-and-run strikes against Indian targets for a dozen years.

"Any militant willing to surrender should not fear or hesitate. Our doors are open for them," an Indian military commander told AFP in Guwahati, capital of the revolt-racked state of Assam bordering Bhutan.

"The surrender offer is now the best possible option for militants fleeing Bhutan. If they try to sneak into Assam, our soldiers will be forced to react."

Assam's state government has published telephone numbers in local media for any militant to call to arrange their surrender when crossing the border.

India has not said what will happen to surrendering rebels but militants in the past giving themselves up have received vocational training and other help.

Indian soldiers claim to have sealed the 262-kilometer (164-mile) border Assam shares with Bhutan to sever rebel lines of retreat.

"The flushing out operations are still continuing with troops in hot pursuit of the rebels who are on the run," a Bhutanese Foreign Ministry official said by telephone from the kingdom's capital, Thimphu.

Bhutan, which launched the crackdown under pressure from its giant neighbour, has said 500 rebels have already surrendered to its soldiers.

India, which helps train Bhutan's army, has said some 100 rebels are in its custody and has reported the deaths of at least 128 rebels and eight Bhutanese troops and logistical personnel since the start of the offensive.

Bhutan has so far given no casualty figures and has rejected a request by the International Committee of the Red Cross (ICRC) to allow a team to visit and possibly help evacuate non-combatants.