Posters have been going up in Saudi Arabia condemning the celebration of birthdays and anniversaries.

According to the religious decree now circulating in the capital Riyadh, it is not permitted to hold parties or exchange presents on the occasion of a person's birthday because this is heresy under Islam.

The decree, which was issued by the highest religious authority in Saudi Arabia, adds that the same prohibition applies to companies and institutions marking anniversaries.

An Islamic scholar in the Saudi city of Jeddah who asked not to be named said he was not aware of any such prohibitions in the holy Koran.

But he said some followers of Saudi Arabia's Wahhabite interpretation of Islam even believed that the celebration of the Prophet Mohammed's birthday was heretical. The prophet's birthday is widely celebrated by Muslims around the world.

In Saudi Arabia religious decrees or fatwas normally carry the endorsement of the ruling al-Saud family.

But there is mounting speculation that the renewed publication of this particular decree, issued three years ago, could be timed to embarrass the government.

On 23 January, Saudi Arabia is due to hold a nationwide celebration to mark the centenary of the conquest of Riyadh by the nation's founding-father, King Abdulaziz al-Saud.

But some maintain that the posters are aimed at Christian expatriates in Saudi Arabia, who have been privately celebrating Christmas and the New Year.