RABAT (AFP) - Sixteen members of Morocco's royal guards died in a road accident on Saturday as they were headed north on a bus to prepare for a visit by King Mohammed VI, medics said.

The pre-dawn accident took place near Al-Hoceima in northern Morocco and wounded 42 other guards, a hospital source told AFP.

They were on board a bus that plunged into a ravine, the source and a local official said, without giving a cause for the accident.

King Mohammed VI, Morocco's ruler since 1999, was on Saturday also to chair a traditional annual ceremony in Rabat marking the anniversary of his accession to the throne.

Known as the celebration of loyalty and allegiance, the ceremony is an elaborate event during which senior government officials and representatives from across the North African country pay allegiance to the king.

But opposition activists are opposed to the event and have called for its cancellation in statements posted on Facebook that have attracted more than 1,000 hits.

Opposition activists have said the annual event perpetuates a "backwardness" and "servitude" in Morocco that is out of touch with the times.