Guwahati: At least 37 people were killed by suspected National Democratic Front of Bodoland (Songbijit) militants in Sonitpur and Kokrajhar districts of Assam on Tuesday evening, police said.

"10 others were also injured in the attack unleashed by heavily armed militants belonging to the Songbijit faction of National Democratic Front of Bodoland(NDFB). Curfew was clamped tonight in areas under four police stations in Sonitpur district," cops added.

According to reports, five people were killed in Kokrajhar, while 30 were killed in Sonitpur at five separate attacks by the militants. The victims were reportedly all from members of tribal communities.

"The attacks by militants of the National Democratic Front of Bodoland (NDFB) faction opposed to peace talks took place in Saralpara village in Kokrajhar district and Santipur village in Sonitpur district," said Inspector General of Police (Law and Order) SN Singh.

He further said, "The militants attacked the villages as a response to the intensified operation by the security forces."

As per reports, the entire state has been put on red alert and the international border between India and Bhutan in lower Assam has been sealed. Counter-insurgency operations have also been launched in the Bodoland Territorial Area District, which comprises the four districts of Kokrajhar, Baksa, Udalguri and Chirang.

Meanwhile, Prime Minister Narendra Modi and Union Home Minister Rajnath Singh condemned the attack.

PM Modi wrote on Twitter - "Killing of innocent people in Sonitpur & Kokrajhar is an act of cowardice. Our thoughts & prayers are with the families of the deceased."

Killing of innocent people in Sonitpur & Kokrajhar is an act of cowardice. Our thoughts & prayers are with the families of the deceased. — Narendra Modi (@narendramodi) December 23,

PM Modi also assaured that Rajnath Singh will travel to Assam and take stock of the situation.

I spoke to Assam CM Shri Tarun Gogoi & Home Minister Rajnath ji. Rajnath ji will travel to Assam and take stock of the situation. — Narendra Modi (@narendramodi) December 23, 2014

“I strongly condemn the killing of tribals in Assam by NDFB militants. Killing innocent people for any cause can never be justified,” Singh tweeted.

I strongly condemn the killing of tribals in Assam by NDFB militants. Killing innocent people for any cause can never be justified. — Rajnath Singh (@BJPRajnathSingh) December 23, 2014

In an another tweet he wrote that the Centre is monitoring the situation in Assam.

The Centre is monitoring the situation in Assam and the paramilitary forces have been rushed to the spot. — Rajnath Singh (@BJPRajnathSingh) December 23, 2014

Home Ministry sources also said it has sought a report from the state government on the series of attacks by the militants.

Additional paramilitary personnel have also being rushed by the Union Home Ministry to Sonitpur and Kokrajhar districts of Assam.

The NDFB had yesterday triggered a grenade blast in Patgaon in Kokrajhar district, injuring three people.

A joint team of Assam Police commandos and the army had on Sunday killed two Bodo militants in neighbouring Chirang district, close to the Bhutan border.

Chief Minister Tarun Gogoi Tuesday said his government will not bow down to any militant threat.

(With Agency inputs)