Saudi Arabian officials have stepped up warnings over plans by women to challenge male-only driving rules, saying that even online support for the protest could bring arrest.
The warnings came on the eve of the planned protest by female activists who have obtained driver's licences abroad.
The internet has been a key tool in reaching out to international media and organising the demonstration, similar to one staged last year by a small group of women in the ultra-conservative kingdom.
Though no specific law bans women from driving, the rules are enforced by Saudi clerics who hold far-reaching influence over the ruling monarchy and give it political legitimacy.
Mention of strict laws against online political dissent significantly broadens the possible fallout from the expected campaign by Saudi women, who have pledged to get behind the wheel tomorrow in defiance of traditions enforced by the nation's powerful Islamic religious establishment.
Today's edition of the pan-Arab newspaper Al-Hayat quotes interior ministry spokesman Turki al-Faisal as saying cyber-laws could apply to anyone supporting the women's campaign.
Conviction can bring up to five-year prison sentences and stiff fines, according to a Saudi consultant on cyber laws, Marwan al-Ruwqi.
Saudi Arabia has adopted some reforms in recent years, including allowing women to sit on the national advisory council and a decision by King Abdullah to permit women to vote and run in municipal elections in 2015.
But the driving ban appears to retain the backing of senior clerics, who also refuse to amend codes such as requiring women to obtain a male guardian's approval to travel.
Mr al-Faisal was quoted as saying the cyber-dissident law "will be applied against violators" while other measures will be taken against "those who gather to support" the planned protest.
He has previously warned of police crackdowns against "disturbing public order". The statement was issued after about 150 clerics and religious scholars protested outside a royal palace, saying Saudi authorities were doing nothing to stop women flouting the ban.
Some of the leaders of the campaign said they received phone calls from authorities emphasising the warnings.
Amnesty International said the main website of the women driving effort, oct26driving.org, ahd been blocked and replaced with the message: "Drop the leadership of Saudi women."
The women activists still plan to defy the driving ban, despite having their campaign website hacked and receiving repeated threats from the authorities to thwart the effort, Amnesty said.
"Saudi Arabian authorities use the excuse that society at large is behind the ban and claim that the law does not discriminate against women. But at the same time they continue to harass and intimidate women activists," said Said Boumedouha, acting director of Amnesty's Middle East and North Africa programme.