Amman - Three Saudi Arabian female activists have been released around a week after they were detained, Amnesty International said on Thursday.
Their release comes one month before lifting a ban on women's driving in the conservative kingdom.
Madeha al-Ajroush, Hessa al-Sheikh and Aisha al-Manea have been freed, the rights group said. However, the circumstances of their release remain unclear.
The three have been vocal in defending women's rights in the conservative kingdom, including protesting a ban on women driving in Saudi Arabia.
Al-Manea, 70, is believed to be the oldest among those detained.
Last week, State Security said seven people were arrested on charges of working with "foreign entities to support their activities."
Local media and international rights groups have identified several women among the seven detained, including activist Loujain al-Hathloul.
It remains unclear if the three women released were among the seven people facing the charges.
The arrests came as Saudi Arabia prepares for the driving ban to come to an end on June 24.
Saudi Arabia is the only country in the world where women were not permitted to drive, though many Saudi women can drive and have licences issued elsewhere in the world.
Women have long campaigned for the right to drive, even organizing a coordinated show of force by driving in the kingdom in defiance of a decades-old ban. Many were detained over the years and were only released after signing a pledge that she would not drive again.
In September, Saudi King Salman repealed the ban, with his son, Crown Prince Mohammed, believed to be behind the move as part of a major liberalization drive in the conservative country.
Saudi Arabia is dominated by the puritanical Wahhabi school of Islam, but the kingdom has been introducing social and economic changes, allowing foreign investments and loosening some laws.