Mumbai: Counterfeit notes being smuggled into India have reached such perfection that even a banker could miss them.

Spotting the difference, especially in the Rs 1000 notes, is a tough ask. The only visible difference between a real and a fake note seems to be the image of Mahatma Gandhi on the watermark that doesn’t seem clear in a fake one.

"The quality of these notes is very good. They are made in a bank note press and even experts can't tell them apart,” says Deputy Commissioner of Police, Mumbai, Brijesh Singh.

The Mumbai police have nabbed four Bangladeshis travelling on genuine tourist visas for carrying Rs 1.28 lakh in fake, right into the heart of India’s financial capital.

These notes are so perfect that they even pass the ultraviolet test and a discerning banker in a hurry wouldn't spot the difference.

The methods of pumping in fake currency is fast changing. Instead of using the Pakistan and Nepal borders, new frontiers are being opened along the porous Indo- Bangaladesh border and larger shipments – some even up to Rs 2 crore – by boat from Sri Lanka.

While police may have foot soldiers like the Bangladeshis and even some mid level operatives, officials say that the mastermind is safe.

The only solution in sight, they say, is plugging the holes in the country's borders.