Thousands of migrants are fleeing Mumbai, Bangalore and other cities in India fearing a backlash from recent violence against Muslims.

Indian Prime Minister Manmohan Singh has moved to reassure migrants from the northeast of the country that they are safe, after rumours of revenge attacks spread panic among people.

Muslims across India have been alarmed by clashes in recent weeks between indigenous people in Assam and Muslim settlers from neighbouring Bangladesh.

At least 75 people have been killed and more than 400,000 displaced.

The mass flight by students and workers back to their homes in Assam, was triggered by widespread rumours that Muslims, a large minority in the predominantly Hindu country, were seeking revenge for the violence.

Talk of revenge attacks has swirled all week, with threats of brutal attacks being carried on social media and mobile phone text messages.

Some websites have fuelled communal tension by misusing pictures of Tibetan monks at a funeral service after an earthquake in eastern Tibet in 2010.

Police in Bangalore sought to scotch rumours of impending revenge attacks, sending a mass text message that told northeastern citizens: "Do not panic or heed to rumour."

Majlis-e-Ittehadul Muslimeen (MIM), a Muslim political party in the southern city of Hyderabad, also assured people they had nothing to fear.

However, some media reports say that up to 15,000 people had left cities in the south and the west.

Railway authorities have laid on extra trains from Bangalore and other cities for the two-day journey back to Assam.

India's post-independence history has been scarred by tension between religious and ethnic groups.

While local tension between Hindus and Muslims has often spread across the country, this is the first time that ethnic unrest in the remote northeast has had a domino effect in mainland India.

Two people were killed and dozens wounded last week when about 10,000 people rioted in Mumbai, the country's financial capital, following a protest by Muslims against the violence in the northeast.