By Subir Bhaumik BBC News, Calcutta

Indian troops have killed 12 fighters from a powerful separatist group in the north-eastern state of Assam in the past two days, the rebels say.

The military chief of the United Liberation Front of Assam (Ulfa) told the BBC that unless the attacks stopped, his fighters would hit back.

The group announced last week that it had formed a team to hold peace talks with the government.

The Indian army says it has no ceasefire agreement with the rebels.

Paresh Barua told the BBC in an interview that the Indian army had attacked at least three Ulfa bases along the border between Assam and Arunachal Pradesh.

'Unfortunate'

He said one of his senior comrades, Achintya Saikia, was among those killed and that another, Prabal Neog, had been seriously injured in the military attacks.

If these military offensives do not stop, we will hit back with all the strength we have Paresh Barua, Ulfa

Mr Barua said it was unfortunate that the army should start attacks against its bases, when Ulfa was in the process of starting negotiations with Delhi.

"If these military offensives do not stop, we will hit back with all the strength we have," Mr Barua warned.

He said Ulfa had stopped its attacks against security forces after its leadership decided to form a committee of 10 civil society leaders.

The Indian army says Ulfa has not signed a ceasefire with the government - so there is no reason for operations against the rebels to cease.

A senior Indian military official said the army had been attacking Ulfa bases for more than three months.