Mass Effect, rated M for mature, allows players to engage in variety of sexual encounters, though non between male and male or male and female.

"This helps to ensure that games are suitable for a general audience and do not feature exploitative or gratuitous sex and violence, or denigrate any race or religion," censors said in an statement.

The offending scene of kissing and heavy petting ends with the female alien saying "by the gods, that was incredible, commander."

A Microsoft spokesman said the publisher respects Singapore's decision to ban the game, which launches on Nov. 20.

Under Singapore law, gay sex is deemed "an act of gross indecency" and carries a maximum sentence of two years in jail if convicted.

Other video games recently banned in the country include God of War II, for nudity, and The Darkness, for excessive violence and offensive expletives.

UPDATE: According to the Straits Times, Singapore censors have reversed their decision. Mass Effect will launch in the country with an M18 rating.