At least 19 people, mostly migrants, were shot dead by tribal separatists in a series of attacks in India's north-eastern state of Assam, news reports said Tuesday, dpa reported.
Police said rebels from the outlawed National Democratic Front of Bodoland (NDFB) targeted a bus Monday night in the Sonitpur district, about 250 kilometres north-east of the state capital, Guwahati, killing eight passengers, the IANS news agency reported.
The victims were taken to a forested area nearby and shot at close range.
"All the dead were Hindi-speaking, hailing from the eastern state of Bihar and were working as government employees," Assam police chief Shankar Baruah told the IANS.
Another group of NDFB militants killed five people, including a woman in a village in Sonitpur, soon after, the Indian Express daily reported.
Later Monday, six more people, including some Hindi-speaking workers, were killed in separate attacks in the Baksa, Karbi Anglong and Sonitpur districts, the report said.
The NDFB is a rebel group that has been fighting for a separate homeland for the Bodo tribe in Assam since 1996.
Police said the NDFB had threatened "revenge killings" last week, saying they would kill at least 20 Indians to avenge the death of a top NDFB militant by security forces last month.
The NDFB suffered a major setback this year when its chief, Ranjan Daimary, was arrested in Bangladesh and handed over to Indian authorities.
Daimary faces a trial in Assam on charges of plotting multiple bombings in October 2008 in which more than 80 people died.
Separatist groups in the north-east have targeted Hindi-speaking migrants from other parts of India in the past.
India's volatile north-east is home to more than 200 ethnic groups and has been plagued by insurgency throughout the past half-century.
An estimated 50 militant groups operate in the north-eastern states of Assam, Arunachal Pradesh, Nagaland, Tripura, Mizoram, Manipur and Meghalaya.