By Subir Bhaumik BBC correspondent in eastern India

Separatist rebels in Manipur in north-eastern India have kidnapped a senior district administration official along the state's border with Burma.

Police said more than 40 heavily-armed rebels ambushed the convoy of Yamben Thamkishore late on Monday and took him away at gunpoint.

Mr Thamkishore was travelling back to Chandel district headquarters, where he is based, from his home in the state capital, Imphal, when the rebels struck.

Twelve of his police guards were also abducted, but subsequently released after their weapons were taken from them.

This is the first time in several years that such a senior government official has been kidnapped in India's troubled north-east.

Ransom demand

Police and intelligence officials believe the Naga tribal separatist group, the National Socialist Council of Nagaland (NSCN), carried out the kidnapping.

At least 11 NSCN rebels were killed in a clash with security forces last week in Chandel district.

The Naga insurrection began in the 1950s

The group blamed the newly elected Congress-led state government for provoking the incident in an attempt to scuttle political dialogue.

The Indian Government has been negotiating with the NSCN for the last four years.

But Mr Thamkishore's family said he was being held by the United Kuki Liberation Front (UKLF), a small rebel group with close links to the NSCN.

His brother Yambem Laba, a member of the Manipur state human rights commission, told the BBC the family had received a ransom demand of three million rupees from the UKLF on Tuesday.

He said efforts were under way to negotiate Mr Thamkishore's safe release.

The complex demography of the state is believed to be at the root of the violence.

In the state's central region, which lies in a valley, a majority of the people are Hindu Meiteis.

But the Nagas and the Kukis - martial tribes with a fierce tradition of clan warfare - control the hills around the valley and make up about 30% of the population.