Saudi authorities have arrested seven women's rights advocates, weeks before the kingdom is due to lift its ban on women driving, rights groups say.
The reasons for the arrests were not clear, but activists say authorities are attempting to silence the women.
The kingdom's state news channel reported that they had been arrested for contacts with a foreign power.
Saudi Arabia has strict laws requiring women to seek male permission for various decisions and actions.
Who are the activists detained?
Seven people in total have been detained, including two male activists.
They include Loujain al-Hathloul and Eman al-Nafjan, who have all publicly opposed the driving ban, which is due to be lifted on 24 June.
According to Human Rights Watch, both Ms Nafjan and Ms Hathloul signed a petition in 2016 to abolish the male guardianship system, which prevents women from travelling abroad, marrying or obtaining a passport without the permission of a male guardian.
Ms Hathloul has been detained twice already, once in 2014 when she attempted to drive across the border from the United Arab Emirates. She served 73 days at a juvenile detention centre as a result, and documented many of her experiences on Twitter.
She was detained briefly again in June 2017 when she arrived at Dammam airport, in the east of Saudi Arabia, but was released several days later.
The Saudi activist was ranked third in 2015's list of most powerful Arab women in the world, and has appeared alongside high-profile figures, such as the Duchess of Sussex, Meghan Markle, at the One Young World summit in 2016 for young leaders.
Ms Nafjan also hit the headlines in 2013 when she filmed another female activist driving through the Saudi capital, before she was stopped by police. Ms Nafjan was released, but refused to sign a pledge that she would not drive again.
What happened to them?
Human Rights Watch says they were all rounded up on 15 May but the authorities have not given a reason for the arrests.
The rights group says the activists had received phone calls from the royal court last September warning them "not to speak to the media".
"The calls were made the same day the authorities announced that they would lift the driving ban on women," it said in a statement.
"It appears the only 'crime' these activists committed was wanting women to drive before Mohammed bin Salman did," Human Rights Watch's Middle East director, Sarah Leah Whitson, said.
Is Saudi Arabia really opening up?
Saudi Arabia lifted the driving ban on women in September last year, with the reform set to come into effect next month.
It is one of a number of recent reforms in the country credited to 32-year-old Crown Prince Mohammed bin Salman, who has spearheaded the Vision 2030 programme to diversify the economy away from oil and open up Saudi society.
His reforms will also allow women to start a business without express permission from a man.
But the changes have not been uneventful. In November last year, dozens of high-profile princes, businessmen and former and serving ministers were rounded up in an anti-corruption drive seen by many as a purge by the crown prince.