New Delhi, Dec. 18: Troops of the Royal Bhutan Army are surrounding and engaging insurgents from India’s northeast in their camps in southern Bhutan and avoiding close-quarters combat, according to an assessment made in the Indian security establishment.

The military operation is the first of its kind undertaken by the Indian Army-trained Bhutan troops.

They have taken casualties and Indian Army and air force helicopters are evacuating them to military hospitals. On Wednesday, the helicopters flew six sorties to Calcutta, presumably ferrying casualties to the command hospital.

Sources in the Indian security establishment said the Bhutan army had thrown cordons around most of the camps and had taken a particularly heavy toll of the National Democratic Front of Boroland with 18 killed and 56 apprehended.

The estimated strength of members in the camps is 400.

The Kamtapur Liberation Organisation, active in west Bengal, had less than 200 activists in the camps, of whom 14 had been apprehended and around 11 killed.

The sources said the yardstick by which the current operation would be judged is the erosion in the Ulfa’s ability to use Bhutan as a launch pad for attacks in India.

The number of Ulfa cadre was probably less than initially estimated and the outfit was already suing for peace and had sent out surrender signals.

They were reportedly unhappy about the poor rations and their morale was low because the top leaders — Arabinda Rajkhowa and Paresh Barua — had fled to Bangladesh or Myanmar before the operations.

The sources said the current leader of the Ulfa in Bhutan, Rajan Neog, was a critic of the outfit’s commander-in-chief, Barua.

Ranged along the border with Bhutan in Bengal and Assam, the Indian Army was a little surprised that there was no inflow of militants into India. This was largely because the camps were inhabited by women and the aged.

The sources said the women and the aged were in the custody of civilian authorities in Bhutan. A flow of Ulfa cadre into India was expected over the next few days, they said.

A scheduled meeting of the cabinet committee on security tomorrow will take stock of the situation arising from the Bhutan army operation and communications with Thimphu.