Four men were arrested on Saturday for allegedly duping a Bowbazar resident out of Rs 9 lakh, which he had transferred to the alleged swindlers through a fake app after being told that the money would be invested in high-return stocks.

Police said the alleged fraud happened in May but was reported to the cops in the first week of June.

"The complainant is a resident of New CIT Road in Bowbazar. He alleged that he was approached by a group of men and convinced to join a WhatsApp group. He was shown forged documents on the letterheads of an American multinational investment bank and Sebi (Securities and Exchange Board of India) to win his confidence," said an officer of the cybercrime cell of Kolkata Police.

Later, he was made to transfer Rs 9.15 lakh through an app, which during investigation turned out to be fake, the police said.

The complainant approached the police when he realised that he had been duped.

The police said they tracked some of the accused men through the bank account where the complainant’s money had been credited.

"We launched electronic surveillance and arrested Mayank Daga, 41, a resident of Nimtala Ghat Street, on July 31. He was remanded in police custody till August 10. Later, we zeroed in on an account in a nationalised bank while searching the money trail," said the officer.

“Other group members — Adit Sarkar, 22, of New Town, Rajat Dey, 35, and Kajal Das, 56 — were traced through the bank account and arrested on Saturday,” the officer said.

Atish Dipankar Dutta, 44, who is suspected to be the mastermind, was also arrested on Saturday. Officers said he was rounded up from the Sreebhumi area under Lake Town police station.

Several mobile phones, other electronic gadgets and forged bank and company documents were seized from the accused, the police said.