Theres no law against women driving in Saudi Arabia - but driving licences are issued only to men.

Authorities have detained six women for driving cars in the Saudi capital Riyadh, in defiance of laws allowing only male motorists on the conservative kingdom's roads.

Saudi Arabia has no formal ban on women driving. But as citizens must use only Saudi-issued licences in the country, and as these are issued only to men, women drivers are outlawed.

Outcry at the segregation, which contributes to the general cloistering of Saudi women, has been fuelled by social media interest in two would-be female motorists arrested in May.

Rasha al-Duwaisi, one of those detained on Thursday, put the ages of the group at between 21 and 30 and said they had met in a district of Riyadh late in the afternoon to teach each other how to drive using three cars.

They were quickly taken to a police station and instructed to summon “male guardians” to collect them from custody.

“It's not the first time we have done this,” Duwaisi said.

“It's my right to drive and my right to know how to drive. I suffer because I can't drive because I have to rely on a driver that I share with four others.”

Many families in Saudi Arabia have at least one driver with an average salary of around 2000 Saudi rials (R3600) a month. Those who cannot afford this assign a male member of family to drive its women, which often amounts to a time-consuming burden.

The interior ministry traffic police could not immediately be reached for comment on Thursday's arrests.

Two of the other detainees were Duwaisi's sisters, she said, adding that she met the other three on Facebook and Twitter.

In May Saudi authorities arrested Manal Alsharif, who posted a YouTube video of herself driving in the kingdom's Eastern Province and calling on other women to do the same.

Alsharif has been released but faces charges of “besmirching the kingdom's reputation abroad and stirring up public opinion”.

Another woman, Shaima Osama, was also arrested in May for driving in Jeddah. She too was later released.

Thousands of Saudi men and women have joined Facebook groups calling for Saudi driving rights to be extended to women.

Women in the country are also required to have written approval from a designated guardian - a father, husband, brother or son - to emigrate, work or travel abroad.

The campaign that Alsharif launched is aimed at teaching women to drive and encouraging them to take to the roads from June 17, using foreign-issued licences. - Reuters