The parliamentary standing committee attached to the Interior Ministry in its report -- presented to both houses of Parliament recently -- said a large presence of illegal Bangladeshi immigrants posed a grave threat to India's security and economy as many border-crossers come with sophisticated weapons and ammunition to fuel terrorism. They also carry a large amount of fake Indian currency to weaken the economy, the report said.

"The government should view the illegal immigration by Bangladeshis seriously," said Sushma Swaraj, a senior lawmaker from the opposition Hindu nationalist Bharatiya Janata Party and chair of the committee that looks into the functioning of the Interior Ministry. "We at the standing committee have recommended that movements of human beings along the border with Bangladesh must be strictly monitored."

In response, the Interior Ministry said it is aware of illegal immigration into India from Bangladesh and has taken measures such as border fencing and floodlighting the area to stem the movement.

With border infiltrations by militants from Pakistan waning, many say India now faces a threat from its porous -- partially fenced -- eastern border with Bangladesh. Intelligence inputs have suggested many illegal migrants have been able to secure ration cards, driver's licenses, voter-identity cards and other government documents.

The Interior Ministry said it has also asked the governments of bordering states to take action to detect foreign nationals in the country illegally -- but this is often hard as Bangladeshis resemble Indians and they usually live in Muslim-dominated parts of India. Bangladesh is a predominantly Muslim country.

India has on various occasions taken up the issue of illegal immigration with Bangladesh, but Dhaka denies a problem exists, India says.

"Illegal migration is a genuine problem, but Bangladesh refuses to recognize it. How this could be solved when Bangladesh does not want to accept it," said Pranab Mukherjee, India's foreign minister.

The presence of fake Indian currency notes in states along the eastern border has alarmed Indian intelligence and security agencies. The gravity of the situation came to light recently when a minister in Tripura state had to resign for alleged links with Bangladesh-based militant outfit Harkat-ul-Jehadi-Islami. India says the group was behind bomb blasts at various places in the country.

The minister, Shahid Chowdhury, told security agencies he supplied at least 20 million counterfeit Indian notes to the markets. Following his confession, security forces swung into action and confiscated a huge sum of fake notes. They refused to divulge the quantity, however.

The government of Assam state, which has among the highest number of illegal Bangladeshi migrants, has set up as many as 32 foreign tribunals for the detention of illegal migrants and foreigners, the parliamentary standing committee said in its report.

The Interior Ministry said the involvement of terrorist groups based in Bangladesh in some incidents of terrorist violence had come to notice, but there were no reports of recruitment of Bangladeshi nationals in India for these purposes. The government has taken various measures to prevent terrorist incidents, the ministry said.

According to a government estimate, India has 20 million illegal Bangladeshi migrants in various states and the capital, New Delhi. The figures provided by Assam's Interior Department said every day around 6,000 migrants from Bangladesh illegally cross the border and enter the state from where they move to other parts of India. Many of these migrants have links to Islamic militant outfits, state police said.