GUWAHATI: India urged Bhutan and other neighbours Friday to help track down separatist rebels who killed 69 villagers in Assam as it stepped up its military offensive in the restive northeastern state.

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.

Foreign Minister Sushma Swaraj sought Bhutan's help to trace the militants amid indications that some of them may have fled to neighbouring countries.

“The minister did take it up with the Bhutanese leadership to seek their support in what we see as a national endeavour to tackle the scourge that is creating a problem there,” ministry spokesman Syed Akbaruddin told reporters in New Delhi.

Swaraj was “assured of support” from Bhutan and is also “working on trying to contact other friendly countries in this context”, he added.

India's northeastern region borders China, Myanmar, Bhutan, Bangladesh, China, and Nepal, and rebels are believed to often criss-cross the thickly forested, mountainous boundaries.

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

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

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

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.

The home minister has vowed authorities will be tough on those behind the killings, which he called “an act of terror”.

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.