Police in Indian city of Bangalore have been placed on alert following a massive exodus from India's technological hub of workers originating from the country's northeastern states, sparked by rumours of an imminent attack on their ethnic group.

"Special forces and commandos are being deployed in areas where north-easterners are concentrated," senior Bangalore police official Vincent D'Souza, said on Saturday.

At least 20,000 natives from the north-east, who have faced discrimination and harassment in the past, have now fled India's southern cities of Bangalore, Chennai, Hyderabad and Pune.

Five people have already been arrested and the police are hunting for four others believed to have spread the rumours via mobile phone text messages and social networks, the IBN Live news channel reported, quoting Karnataka Chief Minister Jagdish Shettar.

The text messages reportedly warned that people from the northeast living in Bangalore would be attacked in retaliation for the killing of Muslims during ethnic violence between Bodo tribals and Muslim settlers in the northeastern state of Assam in late July.

At least 74 people were killed and more than 400,000 fled to government-run relief camps as a result of the violence.

Violent protests by Muslim groups in Mumbai in August have added to the sense of insecurity of the north-easterners.

Top intelligence officials suspect that the rumours, as well as doctored video clips portraying violence against Muslims in Assam, could be an attempt to spark communal tension.

"I was in Bangalore for nine months. I won't go back, even if I don't get work in Assam," an unnamed youth at the Guwahati railway station told NDTV news channel.

Source: Al Jazeera and agencies