Saudi authorities detained a female activist who uploaded a video of herself behind the wheel of a car on to YouTube, in a campaign to overturn a ban on female drivers in the deeply conservative kingdom.

More than 600,000 people have now watched the video, a seemingly mundane scene where Manal al-Sharif, 32, is seen chatting to a female friend as she drives around the eastern city of Khobar.

But the images were anything but mundane in Saudi Arabia, where religious police are charged with ensuring rigid observance of social mores, which include women covering up in public, and no mingling by unrelated members of the opposite sex.

Ms Sharif was initially arrested on Saturday and released after six hours, fellow activists said police came to her home around 3am yesterday morning to take her into detention again.

Ms Sharif, who learned to drive in the United States, has started a campaign through Facebook calling for women to be taught to drive and urging those with international licences to get behind the wheel from 17 June.

Saudi Arabia is the only country in the world which bars women from driving. Although no law forbids it, women are denied driving licences, effectively rendering it illegal. Instead, they must rely on hired drivers, taxis, or male relatives to drive them.

Debate on the driving issue is vibrant, and Saudi women have mounted campaigns to put pressure on the government. Officials have signalled previously that the ban may be lifted, vague pledges that are never followed through.