GAUHATI, India (AP) — A group of rebels using rocket-propelled grenades and automatic weapons ambushed a military convoy in India’s insurgency-wracked northeast on Thursday, killing at least 21 soldiers and wounding 14 others in the latest major attack in the region in recent months, police said.

The ambush occurred as the three-vehicle convoy was on its way from a small town to Imphal, the capital of Manipur state, a police officer said on condition of anonymity because he was not authorized to talk to reporters.

The rebels also used homemade bombs in the attack, setting a truck on fire that was carrying gasoline and diesel fuel in metal containers, he said.

Helicopters carried the injured to hospitals, he said.

The state, which borders Myanmar, has several active militant groups. None immediately claimed responsibility for the attack.

In April, insurgents armed with automatic weapons fired at two trucks carrying Indian paramilitary soldiers in neighboring Nagaland state, killing eight of them.

The mountainous region, known for its natural beauty, has been battling insurgencies for decades.

Most of the main rebel groups in Manipur state are not engaged in cease-fire talks with the Indian government, unlike those in other remote northeastern states.

Separatist groups accuse the Indian government of exploiting the region’s rich natural resources while neglecting local development.

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