Armed men posing as officials from India's central bank have robbed a vehicle transporting 70m rupees ($800,000; £600,000) in the southern state of Karnataka, police say.

A massive operation has been launched to find the men who robbed the van in the heart of Bengaluru city in daylight.

The robbery occurred on Wednesday afternoon. Six men in an SUV stopped a cash transport van on a busy road as it was moving money between bank branches, Bengaluru police commissioner Seemant Kumar Singh told the BBC.

The van was carrying a driver, a cash custodian, and two armed security guards.

Mr Singh says the robbers told the people in the van that they were officials from the Reserve Bank of India and needed to verify if they had the correct documents to transport such a huge amount of money.

The gang instructed the cash custodian and guards to leave their weapons in the van and get into the SUV, while the driver was told to continue driving with the cash.

The SUV followed the cash van for a few kilometers before the gang forced the driver out of the van, made the cash custodian and guards exit the SUV, transferred the cash at gunpoint, and fled.

The area had little CCTV coverage, and police are investigating if the gang used multiple vehicles in the operation.

The cash transportation service company has filed a police complaint.

The SUV used in the heist had a fake number plate and a sticker that read 'Government of India', a police official told the BBC on condition of anonymity.

The official added that police were also investigating any possible connection with employees of the cash transport company.

Karnataka Chief Minister Siddaramaiah told reporters that police have recovered the SUV used in the heist.

However, Home Minister G Parameshwara stated it is not yet clear which vehicle the suspects used to escape.

'It was verified that they changed vehicles and moved the money,' he reported to the media.

He expressed confidence that the police would solve the case soon, as they have with other recent high-profile bank robberies in Karnataka.

In a related incident in May, 59kg of gold worth 532.6m rupees was stolen from a bank using a duplicate locker key, from which police have recovered 39kg of gold and arrested 15 individuals, including two former employees.