Bhutan on Wednesday arrested at least three top insurgents even as its army overran several important bases of anti-India militants in the tiny Himalayan kingdom.

Soldiers overcame stiff resistance and captured the United Liberation Front of Asom's headquarters in the forests at Guabari in the southern part of the country bordering India. The camp housed the ULFA's central training unit and a top insurgency unit.

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The militant outfit's leader Paresh Baruah confirmed the news to journalists in Guwahati and Kolkata.

The Bhutanese army has so far destroyed 17 of the estimated 25 militant camps on its territory. But the biggest break has been the arrest of ULFA's former central publicity chief and think tank member Mithinga Daimari.

"Daimari was arrested in Thimphu. Bhutanese authorities handed him over to their Indian counterparts in Rangia in Assam," Indian Army sources told rediff.com in Kolkata. Eastern Command chief J S Verma had earlier said that ULFA chairman Arobindo Rajkhawa and commander Baruah are in Bangladesh.

Bhutanese soldiers had also arrested Kamtapur Liberation Organisation deputy chief Tom Adhikary and his assistant Milton Varma from the India-Bhutan border. They too have been handed over to Indian authorities and brought to West Bengal.

Reports said KLO chief Jeevan Singh has been killed in an encounter with Bhutanese troops in Samdrup Jonkhar. "We can't confirm that news as yet," Indian Army sources said.

The army action came after ULFA, KLO and National Democratic Front of Bodoland ignored Thimphu's request to leave Bhutan for six years.