Unidentified people have killed five more migrants in Assam, taking to 51 the toll in this week's violence.

Three Biharis drowned in the Brahmaputra river in Tinsukia district after they were thrown in with their hands and feet bound, Inspector General of Police Khagen Sharma said on Sunday.

Two persons were hacked to death in a remote village in Tinsukia, he added.

The violence is believed to have been triggered by an attack on Assamese train travellers in Bihar this month.

This followed reports of attacks on Bihari students who came to Assam to take tests for railway jobs.

Assam is one of India's richest states in terms of resources, especially tea and oil, but residents complain that jobs too often go to people from outside.