Police issued shoot-on-sight orders on Monday in a bid to quell violent clashes in India's remote northeast that have prompted thousands of villagers to flee their homes and left 19 dead.
More than 30,000 villagers have fled amid fighting between Bodo tribal groups and Muslim settlers over land rights, and violence was spreading to new areas, police said.
Soldiers were out in force in the restive state of Assam to try to stop the unrest in which houses have been set ablaze and villagers forced to shelter in government buildings and schools.
"We have just issued shoot-on-sight orders to stop the clashes. Angry residents are burning shops, houses and hostels," S.N. Singh, Assam inspector general of police, told AFP by telephone.
Shoot-on-sight orders are often issued in a bid to restore order when violence spirals.
Singh said the clashes broke out late Friday and had claimed the lives of 19 people and left at least 12 injured.
"Police, army and paramilitary troopers have intensified patrols and a curfew has been imposed in many areas," Singh said, adding there were 30,000 people in the government shelters.
Police said the clashes were spreading to new parts and incidents of arson had escalated.
"We have fled our homes leaving behind everything, fearing an attack on our lives," Pramila Brahma, a mother of four, told a local television channel at one shelter.
"We don't know if at all we can go back to our village as they set ablaze most of the houses," added Habibur Rahman, a casual labourer.
Four bodies were recovered by police on Monday from Kokrajhar district, some 220 kilometres (135 miles) west of Assam's main city of Guwahati.
The fighting, in regions close to the borders with Bhutan and Bangladesh, marks the latest outbreak of violence over long-running territorial disputes.
Many people from both the Bodo and Muslim communities -- particularly women and children -- were seeking safety in designated schools and government offices.
They are protected by soldiers and food is provided.
The Press Trust of India news agency said the fighting was triggered when two Muslim student leaders were shot and seriously injured in Kokrajhar, leading to revenge strikes on Bodo groups.
Rockybul Hussain, the Assam state forest minister, told AFP he was in the affected area and that more security personnel were needed to ensure peace before any villagers started to return home.
"We are appealing for calm and have asked authorities to take adequate security measures," he said.
Kampa Borgoyary, deputy chief of the Bodoland Territorial Council, a local government organisation, said: "There is some panic and people are moving to safer areas apprehending retaliatory attacks."
Northeast India, a remote part of the huge country, has seen decades of friction between ethnic and separatist groups, though some of the biggest rebel movements have recently started peace talks with the government.