Indian Prime Minister Manmohan Singh told Assamese migrants that they were safe, with thousands fleeing major population centers including Mumbai and Bangalore.

Northeastern Indians coming mainly from the state of Assam have been taking flight after rumors of targeted violence against them began to circulate by text message and social media. On Friday, the Indian government banned bulk text messages - to five or more recipients - for the next 15 days.

German news agency dpa cited one member of parliament, Ninong Ering, as saying some 20,000 people had left their homes or were getting ready to do so.

Three weeks of clashes between members of Assam's Bodo tribal community and Muslims have claimed 80 lives. A further 400,000 people have been displaced.

"What is at stake is the unity and integrity of our country. What is at stake is communal harmony," Prime Minister Singh told the upper house of parliament.

"If there are miscreants, if there are people who are fanning these rumors, they should be brought to book."

Investigators follow electronic trail

Some 6,000 people boarded four trains from Bangalore to Assam late on Thursday, a railway source said. At least 5,000 were reported to have left the city on Wednesday.

Similar numbers were reported to be leaving the cities of Hyderabad, Pune and Chennai.

Police and cyber security experts in Bangalore have started work to locate the source of the anonymous messages that have caused the panic.

They say that no attacks on migrants from the northeast, who number 240,000 in Bangalore alone, have been reported.

Assamese migrants are physically distinct from other Indians, looking more East Asian or Tibetan. Large numbers move to central and southern Indian cities to work or study.

rc / slk (AFP, dpa, Reuters)