GUWAHATI: India's army chief pledged Friday to intensify a military offensive in Assam as it tries to track down separatist rebels who killed 69 villagers in the restive northeastern state this week.

India has already deployed 6,000 additional security forces and military helicopters to scour the remote area where armed militants mounted a series of coordinated attacks on tribal villagers on Tuesday.

Police have blamed the attacks on the outlawed National Democratic Front of Bodoland (NDFB), which has waged a violent decades-long campaign for an independent homeland for the Bodo.

“We are definitely going to intensify operations,” army chief Dalbir Singh Suhag told reporters after meeting home minister Rajnath Singh in New Delhi to discuss the security situation in Assam.

The state, which borders Bhutan and Bangladesh, has a long history of often violent land disputes between the indigenous Bodo people, Muslim settlers and rival tribes.

There have been reports of tribal groups armed with machetes and bows and arrows setting fire to houses and shops in Bodo-dominated areas in retaliation for the attacks, in which 18 children were killed.

Another three people were killed on Wednesday when police shot at a mob demanding justice over the attacks at a police station.

Around 7,000 people have fled their homes in the wake of the violence, many seeking refuge in makeshift camps set up by the government.

Home Minister Singh has vowed authorities would be tough on those behind the killings, which he called “an act of terror”.

India's foreign minister has approached the government of Bhutan, where some of the rebels are believed to have fled after the attacks, he said.

Rights groups have in the past accused India's government of not doing enough to tackle violence in the isolated northeastern region, which is home to many marginalised communities.