In a major fraud at the Gurgaon branch of Citibank India, the local police have discovered that a relationship manager for high net-worth individuals stole around Rs 400 crore (Rs 4 billion) from more than 20 clients.

Citibank sources said the fraud was detected only recently and reported to the police.

According to the police, employee Shivaraj Puri had duped HNI clients into investing in Citibank schemes, but their money was diverted to accounts opened in the name of his wife and two other suspects.

The police said they have so far identified 20 clients whose money was siphoned off by Puri, but said there could be many more.

According to the police, Puri's modus operandi used involved using a forged notification of Securities & Exchange Board of India to garner funds, so that the entire transaction looked real.

Investigators said the clients' money is safe. Police have registered a case under Sections 420 and 468 of the IPC. The FIR was filed by Binu Soman, assistant vice-president at Citibank.

Meanwhile, a Citi India statement said it had recently initiated an investigation into certain suspicious transactions, based on documents forged by an employee involving a few accounts at the Gurgaon branch.

It immediately reported the matter to all the relevant regulatory and law enforcement authorities.

"(The) identified suspicious transactions have been isolated. Citi India is providing full assistance to the authorities in their investigations. This issue does not impact other accounts, transactions or customers of the bank," the statement said.

"The banking group has filed a complaint naming the involved employee and other individuals, who appear to be perpetrators of these suspicious transactions.

A senior Reserve Bank of India official said Citi India has to file a special report on the fraud with the banking regulator.

In this report, the bank's headquarter has to provide details, including modus operandi, allegedly used by the employee.