Saudi authorities have arrested an activist who launched a campaign to challenge a ban on women driving in the conservative kingdom and posted a video on the internet of her behind the wheel, activists said.

"Police arrested her at 3am this morning," said Maha Taher, another activist who launched her own campaign for women driving four months ago to spread awareness of the issue.

Women are not allowed to drive and must have written approval from a designated guardian - a father, husband, brother or son - to leave the country, work or travel abroad.

"When the police stopped her they told her she violated the 'norms'. There is no law that says women can't drive in Saudi Arabia and this arrest is unjust. She is a role model for a lot of people and the arrest will provoke her supporters. Now more women want to drive," Taher said.

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