More than 20 people have been killed in southern Bhutan during fierce fighting between government soldiers and Indian separatist rebels.
By Subir Bhaumik
BBC correspondent in Calcutta
The tiny Himalayan kingdom is trying to evict two Indian rebel groups from bases in their country.
At least eight soldiers have died and more than 15 were injured in the fighting, a Bhutan official said.
The rebels say they have suffered 13 casualties and have lost four of their bases in Bhutan.
The operation is the first that Bhutan has mounted against the United Liberation Front of Assam (Ulfa) and another outlawed group, the National Democratic Front of Bodoland (NDFB), who have been sheltering on its soil.
Bhutanese soldiers are continuing attacks against several camps of these two
groups inside Bhutan, the official said.
Indian army helicopters are being used to evacuate the injured, a Bhutanese Government statement said.
Assam Chief Minister Tarun Gogoi welcomed the Bhutanese offensive and urged the rebel groups to stop fighting and hold talks.
"Even Saddam Hussein had to give up. So the Ulfa and NDFB leaders must realise that this is their last chance to start talks with us," Mr Gogoi told the BBC.
Ulfa's military commander, Paresh Barua, told the BBC that two of their
bases in southern Bhutan housing their military and political wings had come
under heavy attack.
He said a senior leader, Bhimkanta Buragohain, had been injured and one
rebel fighter killed.
They said Indian troops had fired on them across the border - but India and
Bhutan deny launching a joint attack.
Bhutan's king told the Indian prime minister of the impending attack
Indian military officials say they have deployed additional troops on the
borders with Bhutan to take on groups of guerrillas who may flee into the
neighbouring states of Assam or West Bengal.
Foreign Minister Yashwant Sinha told parliament: "The Indian army is taking
necessary measures to intercept movement of militants from Bhutan into
He said Bhutan's King Jigme Singye Wangchuk had telephoned Indian Prime
Minister Atal Behari Vajpayee to tell him of the planned action on Saturday.
"Bhutan is now living up to its promise that it will not allow anti-Indian
elements to thrive there," Mr Sinha said.
Under considerable Indian pressure, Bhutanese ministers and officials have
tried to negotiate the rebels withdrawal from the kingdom - without much
Bhutan's National Assembly authorised troops to initiate military action
against the rebels if they did not leave the kingdom on their own.
Thousands have died since the two Indian rebel groups Ulfa and the NDFB took
The NDFB is fighting for an independent homeland for the Bodo tribe in the
north-east Indian state of Assam. The Ulfa is fighting for Assam's
independence from India.
For the past 10 years, the NDFB and the Ulfa have maintained a large number
of bases in southern Bhutan.