Shanghai police have detained 15 people suspected of buying lost identity cards to open "black" bank accounts and then selling the documents, mostly to gangs involved in telecom fraud.

Those involved in the operation purchased ID cards found at waste recycling stations or online and used look-alikes to obtain debit accounts in the card holder's name, according to Xuhui district police.

Xing Yuxuan, a police spokesman, said on Wednesday that the suspects had made about 60,000 yuan ($9,200) in profit.

"It's not an enormous sum," he said, "but telecom fraud－which is what the bank and ID cards were ultimately used for－is hated by the public, as there have been many cases in recent years causing huge financial loss."

In telecom frauds, the victim is usually asked to transfer money to a bank account, with the funds then quickly distributed to several "black" accounts opened with lost or stolen IDs. Xing said such accounts make it hard for police to recover the stolen money.

Police say the Shanghai operation was led by a suspect named Hu, a man born in the 1990s.

Investigations show he purchased lost ID cards and posted ads in online forums and chat groups in November offering part-time work to people who can "help in applying to banks for debit cards". He promised 150 yuan for each successful application.

On Dec 4, Hu and five others were caught by police when they accompanied people they had employed to use lost ID cards to open debit accounts at a bank in the Lujiazui financial area. Police seized more than 100 ID cards and two bank cards.

Hu confessed, according to the police, and later that month another nine suspects who either bought or sold ID cards were detained. "The gang bought ID cards for 50 yuan each, and sold sets of IDs and bank cards for at least 1,500 yuan," Xing said. "They had sold 40 sets in the month before the operation was busted."

He said the operation had been running for three months. Investigations are ongoing into how many sets were sold over that period.

Xing said Hu had told police the success rate in opening debit accounts using the ID cards was about 50 percent, and the rate is generally higher in smaller banks.

"He said when a person they had employed was going to the bank, they'd search for an ID card that carried a picture similar to their face," the spokesman said.

Police have reminded the public to safeguard their ID cards and report lost or stolen cards as soon as possible.