The announcement followed a fresh burst of violence early yesterday when suspected rebels of the National Democratic Front of Bodoland (NDFB) lined up a group of villagers in Assam state's Sonitpur district, some 180km from the main city of Guwahati and opened fire.

Police said six people died and nine were wounded in the attack, which followed a string of rebel-linked bombings and gunfire attacks in Assam and Nagaland states at the weekend.

India's Home Minister Shivraj Patil, after a two-day tour of the flashpoints, promised Monday to send more troops to the region.

"We have instructed additional paramilitary and army columns to be dispatched to Assam following a request from local government," he told reporters at Guwahati airport before flying back to Delhi.

Describing the serial blasts in Assam as acts of cowardice, Home Minister Shivraj Patil said yesterday that the Centre would do everything to support the Assam government and its door for talks with militant outfits like Ulfa was "still open".

"These are dastardly and cowardly acts. Government of India will do everything to help the Assam Government," Patil said at a hurriedly convened press conference in Guwahati.

He said, "if anybody comes with any condition and wants to hold talks, we will not accept. The talks should be held without any condition".

The bloodletting coincides with the 18th anniversary of the founding of the NDFB, one of around 30 rebel groups fighting for greater autonomy or independence in the region.

Patil said New Delhi was open to talks with the rebel groups "although we are committed to taking very strong measures to deal with the spurt in violence.

"Let the militant groups come and talk to us, we are prepared to discuss all issues," he said.

Patil also called for closer inter-state coordination among the troops battling militancy in the northeast and sought the help of locals to deal with militancy, which officials say is aimed at disrupting the peace process underway in the northeast. Civilians are often the targets of the attacks, with the violence Saturday being characterised by three near-simultaneous bomb explosions at a railway station and in two markets in Nagaland's commercial hub Dimapur that killed 50 people.

On Sunday, rebel groups again targetted crowded markets in the region, leaving a further 10 people dead and scores wounded.

Monday's pre-dawn attack was also aimed at civilians.

"The NDFB rebels woke up sleeping villagers and asked them to line up and started firing at them with automatic weapons," a police official told AFP.

"Six people died on the spot and nine more were seriously injured."

Police had earlier reported three rebels killed while trying to plant explosive devices which went off prematurely.

The attacks have shattered the relative calm of mainly agricultural Nagaland, where a truce has been in force with the region's largest separatist group, the National Socialist Council of Nagaland (NSCN), since 1997.