A draconian death penalty policy that targets homosexual acts and adultery has been implemented in Brunei as the tiny sultanate's revised Islamic penal code comes into force despite an international outcry.

The revision of the South-East Asian country's penal code expands the crimes that can be punished by death to include rape, extra-marital sex for Muslims, robbery, and insulting the Muslim prophet Mohammed.

Under the new code, based on the Islamic religious and legal system of Sharia law, the harshest possible punishment for homosexual acts is death by stoning.

His Majesty the Sultan and Yang Di-Pertuan of Brunei Darussalam, Sultan Hassanal Bolkiah, pictured at a Memorandum of Understanding signing with Malaysia, in March. (Getty)

This is reserved for cases where the court believes an especially strict sentence must he handed down.

The threat of the death penalty is apparently chiefly aimed at gay men, although experts are doubtful that executions will actually be carried out.

Sultan Omar Ali Saifuddien Mosque is one of many opulent landmarks in the oil-rich country of Brunei. (AP/AAP)

Gays and lesbians have long faced discrimination in Brunei. The previous maximum punishment for homosexual sex acts was 10 years in prison. Under the new penal code, caning is also a possible punishment.

There has been an international outcry against the revisions championed by Brunei's ruler, Sultan Hassanal Bolkiah.

Brunei's tiny position in the world - and even on Borneo - can be seen (inside the smaller of the two white lines on the central island) bordering Malaysia, which in turn borders Indonesia. (UNIVERSAL IMAGES GROUP)

Human Rights Watch has called Brunei's revised penal code "barbaric to the core" for "imposing archaic punishments for acts that shouldn't even be crimes."

Hollywood star George Clooney has called for a boycott on luxury hotels owned by the sultan.

Currently only Saudi Arabia, Iran, Mauritania, Sudan and Yemen have laws in force that punish homosexuality with death, even though it appears that such sentences have not been carried out in recent years, according to UN rights spokeswoman Ravina Shamdasani.