A woman being treated at a hospital after she was injured in an attack by suspected Bodi militants in Assam (Press Trust of India photo)

At least 52 people were killed in a series of coordinated attacks by suspected Bodo militants in Assam on Tuesday.Men, women and children were shot dead with AK-47 bullets in five attacks, the police said. Some 35 people were killed in the Sonitpur district and 14 at Kokrajhar.Those killed were mostly tribals who worked in tea gardens in the region.Prime Minister Narendra Modi has called it an "act of cowardice". In a tweet this morning, President Pranab Mukherjee said, "Such acts of terror and violence must be put down with a firm hand."In one village in Sonitpur, 27 people were killed. "They didn't even spare women and children," a police officer said. 10 women and 13 children are among the dead.Villagers who escaped told the police that the attackers came on foot, armed with assault rifles and wearing military uniforms. They forced open the doors of their thatched huts and started firing. Some people were dragged out of their homes and shot at point-blank range.Home Minister Rajnath Singh will visit the state today.The police suspect the involvement of a breakaway faction of the National Democratic Front of Bodoland, which has been fighting for a separate homeland for decades. The Bodos are an indigenous tribe in Assam, making up 10 percent of the state's 33 million people.

The police say the attacks could be motivated by revenge. Lately, the group has suffered heavy casualties in a crackdown by security forces. Two militants were killed in the last encounter with soldiers on Sunday.The police also say the attack could be a tactic to strike terror ahead of the elections to the Bodoland Autonomous Hill Council. The Bodo militants accuse tribals of helping the security forces.Assam is on red alert and a part of the international border with Bhutan has been sealed. Counter-insurgency operations have been launched in the Bodoland Territorial Area District that spans Kokrajhar, Baksa, Udalguri and Chirang.