DUBAI, United Arab Emirates — A Saudi woman detained for defying the ultraconservative kingdom's ban on female drivers was released Monday after growing international pressure for her freedom, a rights activist said.

The 32-year-old woman, Manal al-Sherif, became the centre of a growing Internet campaign that also served to draw attention to plans for a June 17 rally calling for a mass driving protest to challenge the restriction.

The Saudi activist, Waleed Aboul Khair, credited al-Sherif's release on "pressure from inside and outside" Saudi Arabia, which follows an austere brand of Islam known as Wahhabism that is enforced by morality police.

Al-Sherif had been detained since May 21 after posting an Internet video of her driving as part of a campaign for the planned protest next month. She was ordered to remain in custody until at least early June.

The reason for the early release was not announced by authorities, but Aboul Khair said al-Sherif signed an agreement not to attempt to drive again or speak to reporters.

Even so, Aboul Khair said he still plans to press ahead with a petition asking Saudi authorities to lift the driving ban on women -- the only such rule in the world.

There is no written Saudi law banning women from driving -- only fatwas, or religious edicts, by senior clerics. They claim it protects against the spread of vice and temptation because women drivers would be free to leave home alone and interact with male strangers. The prohibition forces families to hire live-in drivers or rely on male relatives to drive.

King Abdullah has promised some social reforms, but he depends on the clerics to support his ruling family and is unlikely to take steps that would anger the religious establishment.

Al-Sherif's Facebook page, called "Teach me how to drive so I can protect myself," was removed after more than 12,000 people indicated their support. The campaign's Twitter account also was blocked. Hundreds of other sites have sprouted to support her and the protest call.