RIYADH, June 29 (Reuters) : Saudi Arabian police detained five women for defying the conservative kingdom's driving ban, an activist said on Wednesday, although police said they had detained only one.

"All the cases were in Jeddah and we were really surprised to hear this because this was not the case before," said Saudi activist Eman al-Nafjan.

Authorities have appeared to allow driving this month by dozens of women who answered a call from groups, including "Women2Drive" and "Women's Right to Drive in KSA", to challenge the ban. Many posted accounts of their driving on the Internet.

A police official in Jeddah said only one woman, who was driving with her brother in the Red Sea port, had been detained.

"I only know about this one case, the rest I have no information about," the official told Reuters.

Although there is no written law against women driving, they are not issued licences, effectively banning the practice.

Women in Saudi Arabia must also have written approval from a male guardian -- a father, husband, brother or son -- to leave the country, work or even undergo certain medical operations.

Ruled by an absolute monarchy supported by conservative Wahhabi clerics, Saudi Arabia is a conservative country where religious police patrol the streets to ensure public segregation between men and women.

Two women, Shaima Osama and Manal Alsharif, were arrested for defying the driving ban this month.