New Delhi  - At least 10 people were killed and 12 wounded in an attack by tribal separatist militants in India's north-eastern state of Assam, officials said Monday.

A military operation was launched after heavily-armed rebels of the National Democratic Front of Bodoland (NDFB) attacked a village in Sonitpur district, some 240 kilometres north of state capital Guwahati Sunday night.

"A group of NDFB militants fired indiscriminately, killing locals who apparently defied their extortion demands. Ten villagers were killed at the scene," local police officer P Rehman said in a telephone interview.

Three women and two children, a girl and a boy, were among the victims. "The death toll could rise as seven of the twelve injured are in a serious condition at the hospitals," he added.

Following the attack, soldiers accompanied by police commandoes and paramilitary Assam Rifles forces were conducting an operation in the region to track the militants.

The situation was tense as villagers were armed with bows and arrows, machetes and spears. Additional police were deployed in the village.

Police said the militants had made extortion demands of up to 100,000 rupees (2,100 dollars) to individual villagers who had refused to pay.

The attack came a day after the militant outfit observed their 23rd anniversary and issued a threat to the security forces.

The NDFB is a rebel group which has been fighting for a separate homeland for the Bodo tribe in Assam since 1996. Although a faction of the NDFB had agreed to a ceasefire with the Indian government since 2005, another group is still carrying out violent attacks.

India's north-east, which shares borders with China, Myanmar and Bangladesh, is a volatile region where nearly 40 separatist, tribal or leftist groups are active in five states. More than 15,000 people have been killed in the region in the past decade. (dpa)