Guwahati: Ten railway workers were killed by tribal separatists in India's restive north-eastern state of Assam, officials said Sunday.

A police spokesman said a heavily armed group of militants from the Jewel Gorlosa faction of the outlawed Dima Halam Daoga (DHD), popularly known as the Black Widow, attacked Sunday a railway construction site near village Phainagar in North Cachar Hills district, about 310 km south of Guwahati.

"Seven people, all workers at a railway construction site, were killed on the spot when Black Widow militants fired indiscriminately with automatic weapons," S. Singh, a senior police official, said.

The same rebel group late Saturday killed three railway construction workers at village Migrain Bisu in North Cachar Hills district.

"The militant group earlier Saturday had asked railway construction work to be stopped immediately," another police official said.

On Saturday, the Black Widow group claimed 12 of its cadres were killed by army soldiers in the district during an anti-insurgency operation.

The army, however, denied the reports.

"There was an encounter, no doubt, Saturday. But we have absolutely no report of any casualties or bodies of militants being recovered so far, although some news agencies and television channels did report about 12 Black Widow rebels (being) killed," army spokesman Colonel Rajesh Kalia told IANS by telephone from the Four Corps Headquarters in Tezpur in northern Assam.

The Black Widow is a rebel group fighting for an independent homeland for the Dimasa tribe in the region.