Saudi Arabia braced for possible protests after women activists declared an "open driving campaign" against the deeply conservative kingdom's ban on women behind the wheel.
Activists had originally planned a "drive-in" on Saturday but cancelled it after threats of legal action, instead declaring an open-ended campaign in the only country that forbids women from driving.
"Out of caution and respect for the interior ministry's warnings... we are asking women not to drive tomorrow and to change the initiative from an October 26 campaign to an open driving campaign," activist Najla al-Hariri told AFP news agency on Friday.
It is known that women in Saudi are banned from driving and laws will be applied against violators and those who demonstrate in support.
Several women said they had received telephone calls from the ministry, which warned of measures against activists who chose to participate and asked them to promise not to drive on Saturday.
"It is known that women in Saudi are banned from driving and laws will be applied against violators and those who demonstrate in support" of this cause, ministry spokesman General Mansur al-Turki told AFP.
On Wednesday, the ministry said it would act against anyone who attempts to "disturb public peace" by congregating or marching "under the pretext of an alleged day of female driving".
In remarks to the Al-Hayat daily published Friday, Turki even warned against supporting the campaign online.
Activists have repeatedly insisted that no demonstrations will be held in the absolute monarchy, which officially bans public gatherings.
Amnesty International has denounced the threats, while Human Rights Watch called for an end to discrimination.
Said Boumedouha, Amnesty's acting Middle East and North Africa programme director, said Saudi authorities "continue to harass and intimidate women activists".
"This has included phone call and online threats, arbitrary travel bans and detentions, forcing activists and their family members to sign pledges not to drive and using the state-controlled media to discredit activists."
London-based Amnesty said "the ban and the ongoing scare tactics to maintain it are out of step with the modern world, and characteristic of the wider discrimination that crushes women's freedom and besmirches the kingdom's reputation".
The UN Human Rights Council has also urged Saudi Arabia to end discrimination against women, among other rights abuses.
Over the past two weeks, videos posted online have shown women already driving in Saudi Arabia, but women who have defied the law in the past have run into trouble with the authorities.
In 1990, authorities stopped 47 women who got behind the wheel in a demonstration against the driving ban In 2011, activist Manal al-Sharif, one of the organisers of Saturday's campaign, was arrested and held nine days for posting online a video of herself behind the wheel.
That year Saudi police arrested a number of women who defied the driving ban and forced them to sign a pledge not to drive again.