Egyptian activist Sanaa Seif was detained on Tuesday after the public prosecution issued a warrant for her arrest based on investigations by the national security apparatus, which revealed that she was “spreading false news and rumours” on social media, the prosecutor-general’s office said.

Seif was apprehended on Tuesday afternoon and ordered detained for 15 days pending investigation into charges including “broadcasting false news, statements and rumors aiming to disturb public security and peace” as well as “promoting ideas that call for committing terrorist acts,” the prosecutor’s office said in a statement late on Tuesday.

The statement said that Seif, the sister of prominent jailed activist and blogger Alaa Abdel-Fattah, aimed to “spread false news about the deteriorating health conditions in the country and the spread of the coronavirus in prisons,” and called for demonstrations that would “incite public opinion against the state” to force it to free prisoners.

Seif was acting as part of a plot hatched by a number of fugitives living aboard who seek to incite chaos in the country and undermine security and peace, the prosecution said.

Seif has denied the charges leveled at her, the statement added.

Seif, along with her sister Mona and their mother Laila Souief, was staging a sit-in on Monday night in front of Cairo’s Tora prison complex to demand the family be allowed to receive a letter from Abdel-Fattah, with whom they had not communicated in three months due to the coronavirus outbreak.

Mona said in a video released on Tuesday that during this sit-in, they were attacked by a group of women who beat them with sticks and stole their personal belongings while prison security forces failed to intervene.

Mona also said in the video that her sister was abducted by plain-clothes police from outside the prosecutor-general’s office in New Cairo, where she had gone to file a report about the assault.

The prosecution said that Seif was apprehended in accordance with an arrest warrant issued against her.

The prosecution also ordered that Seif be checked by a prison doctor to determine the condition of her health as well as be examined by the forensic medical department to determine how and when her injuries were sustained.

A number of local human rights organisations have released a joint statement condemning the “arbitrary detention” of Seif, demanding her immediate release and calling on prosecutors to investigate the assaults against her and the “inaction” of the prison security personnel during the assault.

The signatory NGOs include the Association for Freedom of Thought and Expression, El-Nadim Centre, the Egyptian Front for Human Rights, and the Egyptian Commission for Rights and Freedoms. 

London-based Amnesty International has also condemned Seif's arrest.