The death toll in Assam's Udalguri and Darrang districts, dogged by clashes between Bodos and illegal Bangladeshi migrants, rose to 40 today with the violence spreading to neighbouring Chirang district.

Miscreants killed two people, including a pregnant woman, and injured two others in Chirang district, which led to blockade of the National Highway 31(C) by Bodo protesters, the police said.

The death toll now stood at 40 with 15 people dying in police firing alone, Chief Minister Tarun Gogoi told reporters here.

"Five hundred houses had been set ablaze so far and over one lakh people had taken shelter in relief camps," Gogoi said.

Four companies of BSF were deployed in violence-hit areas and two more companies were on their way, he said.

He added that helicopters were patrolling to spot mobs in the troubled areas where shoot-at-sight orders were in force.

No fresh incident was reported from worst-hit Udalguri and Darrang districts where indefinite curfew had been clamped with the army staging flag marches.

The Chief Minister, who had yesterday claimed that a section of NDFB cadre could be behind the violence, asked the outfit, which is under a ceasefire agreement with the Centre, to stay in their designated camps.