In a communication to all states, the Union home ministry said the rise of terrorism in last few decades has become a serious concern for most nations as illegal migrants are more vulnerable to getting recruited by terrorist organisations.
"These illegal immigrants not only infringe on the rights of Indian citizens but also pose grave security challenges," the communication, sent last week, said.
Infiltration of (the Rohingiyas) from Rakhine state of Myanmar into Indian territory, especially in recent years, besides being burden on the limited resources of the country also aggravates security challenges posed to India, the home ministry said.
Union minister of state for home Kiren Rijiju had said in Parliament on August 9 that according to available data, more than 14,000 Rohingyas, registered with the UNHCR, are presently staying in India.
"However, some inputs indicate that around 40,000 Rohingyas are staying in India illegally and the Rohingyas are largely located in Jammu, Hyderabad, Haryana, Uttar Pradesh, Delhi-NCR and Rajasthan," he had said.
On November 16, 2016, the government had informed the Parliament that according to available inputs, there were around 20 million (two crore) illegal Bangladeshi migrants staying in India.
The home ministry communication said India is a large country having its border with many countries. People in the sub-continent have a common history and share many similarities in physical looks.
"Due to a variety of reasons, including political and economic turmoil in neighbouring countries, people from such countries often enter India. There are cultural and ethnic similarities, on many occasions such migration goes unnoticed and they settle in Indian territory," joint secretary in the home ministry Dilip Kumar said in the letter sent on August 8.
The Centre also directed the state governments to set up a task force at district level to identify and deport illegally-staying foreign nationals.