The accident happened on Friday night when their open truck smashed into a car on the road between the tiny kingdom's two main cities, Mbabane and Manzini, en route to the traditional Reed Dance.

"Thirteen people have died and the toll hasn't risen" since the accident, police spokesman Khulekani Mamba told AFP.

Local media gave the same death toll, but pro-democracy activists from the Johannesburg-based Swaziland Solidarity Network said 65 were killed.

Eleven of the victims were girls from the village of Phonjwane in eastern Swaziland, according to the daily Times of Swaziland.

The Reed Dance, due to be held on Monday, is a beauty pageant that attracts tens of thousands of young virgins who dance before the polygamist king, who can select one of them as a new wife.

Mswati, Africa's last absolute monarch, chose his 14th wife at the celebration in 2013.

King Mswati said the girls' deaths were a "tragedy in the nation".

"I would like to assure the parents who have lost their loved ones that the nation will support them through and through," the monarch, speaking on the sidelines of a trade fair in Manzini, said.

"Also those in hospitals, should the need arise for further treatment they will be taken to other hospitals to ensure no further loss of life."

News of the accident has not been broadcast on public television and journalists were blocked from photographing the crash scene, a local journalist said.

Swaziland Solidarity Network activists claimed the ruler had fabricated the lower death figure.

"It's lies. This puts the king in an embarrassing situation and he is trying to undermine the toll," SSN spokesman Lucky Lukhele said.

Mswati III has ruled Swaziland as an absolute monarch since his father's death in 1982.

AFP