Guwahati - Police used helicopters to spot armed mobs attacking Muslims in India's troubled northeast on Tuesday, where clashes between indigenous tribesmen and settlers have left 47 people dead and tens of thousands homeless. Police said four people died from their wounds overnight. More than 85,000 people have lost their homes and are being sheltered in government camps after the clashes broke out last week between mainly Hindu tribesmen and Muslim Bangladeshi settlers in the oil and tea-rich state of Assam. "At least 47 people had lost their lives so far," said R.N. Mathur, Assam's police chief. Muslims have responded with some violence as well, he said.

The clashes have reignited a long-simmering conflict as local Assam tribes, mainly Hindu but with some Christians, fear being overrun by Muslim immigrants. More than 40 percent of Assam is now Muslim, mainly immigrant settlers.

The violence is some of the worst since 1983, when more than 2,000 people, mainly Bangladeshi immigrants, were killed in clashes with tribal peoples in central Assam.

The current conflict was sparked by an increasingly strong student movement that has been campaigning against immigrants, analysts say.

Police said fresh clashes were being reported from southern Assam where at least 25 rubber plantation workers were attacked by Muslim settlers in Goalpara district.

Mathur said an additional 500 federal police had been deployed in the state where hundreds of security forces were already trying to control the situation.

He said helicopters were being used to spot movement of mobs in remote areas.

"It is not possible to have static security posts in each and every village, so we have intensified patrolling in remote areas," said Himanta Biswa Sarma, a minister supervising security and relief measures.

These clashes are the latest bout of violence to hit India. In the eastern Orissa state, clashes between Hindus and Christians over conversions have killed at least 36 people.

In Assam, officials have blamed the National Democratic Front of Bodoland (NDFB), a tribal separatist group, for being behind the violence. Security forces have caught four NDFB militants with weapons in the violence-hit area.

The NDFB, a largely Christian group, has held to a ceasefire with New Delhi over the past few years and has denied the charge. Tribal groups blame New Delhi for neglecting their welfare, ignoring development of the region and flooding the area with outsiders.

Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 tribes and has been racked by separatist revolts since India gained independence from Britain in 1947.