Two security vehicles arrived at Mariam’s home on Wednesday morning and took her away, her sister Rabah Sadiq al-Mahdi told Reuters, a day after Sudan’s security chief ordered the release of dozens of detained protesters.
Mariam, a medical doctor, is the deputy head of the opposition Umma Party which her father Sadiq al-Mahdi heads.
The interior ministry could not immediately be reached for comment.
Sudan has been gripped by a wave of anti-government protests that began on Dec. 19. Rights groups say at least 45 people have been killed. The government puts the deathcount at 30.
Sadiq al-Mahdi returned to Sudan last month from nearly a year in self-imposed exile and called for a democratic transition before thousands of supporters.
He was overthrown in 1989 by an alliance of Islamists and military commanders that still form the nucleus of President Omar Hassan al-Bashir’s all-powerful National Congress Party.