Singapore: A Singapore immigration official was Thursday charged for allegedly receiving sexual favours from Chinese women in exchange for helping them extend their visas, a rare case of corruption in a city-state known for its clean image.

Chin Peng Sum was also accused of tipping off the two women about impending raids and obstruction of justice for deleting incriminating text messages that he had exchanged with them.

The 51-year-old, a staff sergeant with the Immigration and Checkpoints Authority, allegedly accepted sex as bribes from the foreign women in exchange for ensuring that their visitor passes were extended, the country's anti-corruption body said.

He was also accused of violating the Official Secrets Act by informing the women in advance about impending raids so that they could evade arrest for "vice-related and/or immigration" offences, the Corrupt Practices Investigation Bureau added.

"It is a serious offence for public officers to act in their own interests and use their position to solicit corrupt benefits," it said.

Singapore, a thriving business hub and financial centre, takes a tough stand against graft, and has consistently ranked in surveys as among the least corrupt countries in the world.

Its civil servants' salaries are among the highest in the world, in what authorities say is a bid to deter corruption.

Cases do still occur sometimes. In 2013, Peter Lim -- former head of the civil defence force, which oversees emergency services -- was found guilty of corruption in a sex-for-contracts case and jailed for six months. (AFP)

Also Read: First in Asia: Facebook Mulls Singapore Data Centre