"We will also work as quickly as possible to seal the border between India and Pakistan."

Border problems

Indian Home Ministry spokesman K.S. Dhatwalia told CNN the government plans to seal the "line of control," the border between India and Pakistan in Kashmir.

Tripathi estimated there may be as many as 15 million illegal Bangladeshi immigrants living in India.

Much of the existing border is already secured, Dhatwalia said. The current effort is to seal off the remaining 10% which the government has yet to be able to secure.

"It's a very difficult terrain," he said, adding that the government plans to finish the project by the end of 2018.

Breaking the seal

Analysts however, are far less confident than the government, saying the difficult terrain on the two borders makes securing them nearly impossible.

"These are permeable borders, you cannot seal them off no matter how hard you try, no matter what high technologies you try to import," said Bharat Karnad, a national security expert at the Delhi-based think tank the Center for Policy Research.

Karnad said there are areas of Kashmir where heavy snow wipes out any fences that are built, while the Bangladesh side is littered with marshlands and rivers.

Ajai Sahni, executive director of India's Institute for Conflict Management, said however permeable borders may be, fencing and other security measures do have an effect.

After India and Pakistan signed a ceasefire agreement over Kashmir in 2003, Sahni said, India constructed wire fences along the highly-militarized "line of control," significantly cutting down on the flow of illegal migrants.

A spokesman for the Indian Border Security Force -- which jointly patrols the "line of control" with the Indian army -- said that it has more than 250,000 troops, making it the world's largest border force.

"Infiltration does continue, but it's not as easy as it was," Sahni said.