Beware of criminals posing as police officers offering to help get an arrested friend or relative released from custody in exchange for cash - it's a scam.

That's the warning issued on Thursday by police who said the scam had emerged over the past few weeks in the Eastern Cape.

"These faceless criminals are phoning relatives of the arrested suspects whom they know are desperately seeking help to have their loved ones or friends released from police custody," said police spokesperson Brig Tembinkosi Kinana.

"These heartless and unscrupulous individuals pretend they are bringing solutions to cases that are being investigated by the police."

The criminals use fake names and ranks, introducing themselves as senior police officers who can help, in exchange for money.

He said only a court could order the release of a suspect from custody, and only under certain conditions.

"This therefore means that no third person may be involved or communicate on behalf of the complainants, relatives or accused persons other than their legal representatives.

"The SAPS is not a money-making organisation but a government institution which renders its services free and without conditions or strings attached."

The Hawks arrested three of their own in Pretoria in April for their alleged involvement in crimes related to corruption, extortion, intimidation and defeating the ends of justice.

It was alleged that the three officers had visited a business in January where they allegedly extorted a large sum of money from the owner.

They took the money in exchange for not reporting the business for being in possession of false documents.