At least seven bank customers have lost Sh600,000 to a gang of four in three days.
Police, unable to track down the gang, now urge the public to be more vigilant.
Central police officer Patrick Oduma on Monday said they had profiled the Nairobi gang, which includes rogue police officers.
“We even have information that they are looking for money to bail out their colleagues who are in prison remands over other serious offences,” said Mr Oduma
The gang members are armed and have handcuffs and a police radio.
On Monday, a businessman was robbed Sh400,000 when the gang confronted him at the parking yard. He had just left a bank on Kenyatta Avenue where he withdrew the cash.
“I had just put the money in the car when I was confronted by three men, one in police uniform. One of them just went for the rear seat and picked up the bag containing the cash,” said the victim.
Police also report that on Saturday at around 10am, Mr Francis Mutiti withdrew a total of Sh180,000 from two different to buy some items along River Road.
While walking along Tom Mboya Street, he was confronted by four armed men who handcuffed him and forced him into the vehicle.
He was later dumped along Kiambu Road after being robbed of the cash, mobile phone, cheques, and other valuables.
An hour later, Mr Charles Kyalo withdrew Sh70,000 from a bank at the junction of Moi and Haileselasie avenues. As he was crossing Moi Avenue, he was confronted by three men, one in police uniform.
They asked him for his ID card but before he could produce it, he was forced into an awaiting vehicle. They handcuffed him and later abandoned him within Muthiaga after robbing him of the cash and other valuables.
On the same Saturday afternoon, a University of Nairobi student, Mr Joshua Muli was robbed of Sh352,000 which he had withdrawn from a bank on Moi Avenue.
As he was crossing the road, he was confronted by a gang, believed to be the same one that attacked Mr Kyalo, who forced him into an awaiting car. He was later dumped at Kamiti corner.
Police suspect the gang members have informers inside the bank who alert them of customers who withdraw large amounts of money. In other cases, they pretend to be customers in the bank and would usually stand in the queue.