The operation involves hundreds of soldiers on foot with the support of helicopters in the remote mountainous forests close to the border with Myanmar, where insurgents are demanding autonomy for their tribal groups or independence, said Army and intelligence officers.

The Central Government asked the Army to "trace and eliminate the insurgents" involved in the attack, a military commander said, asking not to be identified because he is not authorised to speak to the media.

As in much of India's remote and underdeveloped northeast, Manipur has been the scene of recurring strife between ethnic and religious groups since independence from British rule in 1947.

Manipur is one of seven northeastern provinces attached to the rest of the India by a thin strip of territory arching above Bangladesh.

A senior intelligence officer said about 50 tribal guerrillas were involved in the ambush of the three-vehicle convoy on a narrow road on a remote hillside about 100 km (60 miles) from the state capital, Imphal, yesterday.

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