India has accused Pakistan of fabricating threatening bulk messages that triggered panic among migrant workers in southern Indian cities.
Thousands of people hailing from indigenous communities in the northeastern state of Assam fled Bangalore and Mumbai on Saturday and earlier days.
The messages threatened revenge attacks against them by Muslims after ethnic violence in Assam pitted the Bodo tribe against Muslim settlers, leaving more than 80 people dead and displacing more than 400,000.
"The bulk of these messages, of these clips, have their origin in our western neighbour, in Pakistan," Raj Kumar Singh, Indian interior minister, said.
"That's what our agencies have discovered: that the bulk of these have been uploaded in various websites in Pakistan."
He said a number of photographs purportedly showing people killed in revenge attacks for violence in Assam were actually doctored pictures of victims of natural disasters.
Singh said India would register a formal protest with Pakistan.
"We will raise this issue with Pakistan... I am certain that they will deny out of hand but our technical people are definite," he said.
India has banned bulk text messages temporarily to try to halt the spread of threats and incendiary rumours. Police in southern city of Bangalore have also arrested three people for spreading images and video clips across India.
The images of atrocities allegedly on Muslims sparked tension and people hailing from the northeast were attacked in western and southern cities.
Prime Minister Manmohan Singh said those who were fanning the rumours should be punished, saying "communal harmony" was at stake.
India and Pakistan have fought three wars since independence in 1947, two of them over the Himalayan region of Kashmir, which is divided by a heavily militarised Line of Control and which both countries claim in full.
Last year they resumed their tentative peace process, which collapsed after Islamist gunmen from Pakistan killed 166 people in Mumbai in November 2008.