Eleven people, including a lawmaker and four of his family, were killed in an ambush by tribal separatists in the eastern Indian state of Arunachal Pradesh, a senior police official said on Tuesday.

Heavily armed militants fired automatic weapons at the five-vehicle convoy of Tirong Aboh, a member of the legislative assembly for the state seat of Khonsa, in the Tirap district near the border with Myanmar, the police official said.

“We are yet to ascertain the group responsible for the attack,” the police official, who declined to be named as he is not authorised to talk to the media, told Reuters.

The area where the ambush took place is very remote, making an investigation of the attack difficult, the official said.

“Extremely shocked by unfortunate incident of killing of Khonsa MLA Tirong Aboh along with several others by insurgents,” Arunachal Pradesh Chief Minister Pema Khandu tweeted.

Attacks on Indian officials by separatist militias have declined in recent years, though dozens of groups still operate in north and eastern areas of the country.

In April, five people including a lawmaker from India's ruling party were killed in the eastern state of Chhattisgarh when Maoist militants detonated a bomb as an entourage travelled back from a campaign appearance.