"Four persons were killed in police firing this morning when they were indulging in violence in the Rampur and Chaparkata areas of Kokrajhar," IGP, Bodoland Territorial Areas District (BTAD), S N Singh told PTI.
Sporadic incidents of violence and arson were reported from Kokrajhar, Chirang and Dhubri districts, while the situation was tense in neighbouring Bongaigaon and Udalguri districts.
Bongaigaon and Udalguri districts fall under the BTAD.
Around 70 houses in four villages at Bijni in Chirang district were torched. Over 50,000 people are housed in relief camps.
There were reports of violence spreading to Sonitpur district in north central Assam also.
Shoot at sight orders and indefinite curfew continued in Kokrajhar, where the army was deployed, while night curfew was in force in Dhubri and Chirang districts, official sources said.
Miscreants pelted stones and attacked the Guwahati-bound Rajdhani Express at Gossaigaon in Kokrajhar district damaging four coaches though there was no injury.
The train was turned back and was halted at Kamakhyaguri station bordering West Bengal with the authorities considering to take it to Coochbehar.
Prime Minister Manmohan Singh called up Assam Chief Minister Tarun Gogoi during the day and directed him to do everything possible to control the violence. (MORE)