The ‘Coalition for Women in Journalism’ said it is “appalled” by the detention of the journalist and urged the Egyptian authorities to release her immediately.
“Journalism is a tool that helps both the public and authorities to keep everyone accountable. Journalists like Basma are essential for transparency and accountability in the state. The state should cherish and support them instead of targeting and detaining them,” the organisation said.
“Independent journalists in Egypt often face such charges for covering stories concerning state and military misconduct,” the statement added.
Mostafa was brought before prosecutors on Sunday after going missing a day earlier as she reported on unrest in the village of Al-Awamya.
Her detention happened as she reported on the alleged killing of a man, by police, during the demonstrations, according to her employer, the Al-Manassa news website.
“The prosecution ordered that she remains in jail for 15 days pending an investigation over charges of joining a terrorist group and spreading false news,” her lawyer Hala Doma wrote on Facebook late Sunday.
Dozens of Egyptians took to the streets in several villages across the the country in September, according to videos shared widely on social media.
The demonstrations coincided with mounting anger, particularly in rural and low-income areas, over sweeping government campaigns against illegal construction, which have forced people to pay fines to legalise home ownership.
They came after exiled businessman Mohamed Ali, who has emerged as a vocal critic of President Abdel Fattah al-Sisi since last year, called for protests against the government.
On Friday, London-based rights group Amnesty International said Egypt had arrested hundreds of people, and that security forces had killed at least two during the demonstrations.
Sisi, on Sunday, warned against attempts to stoke instability in the country. The general-turned-politician said the government was carrying out the campaign against illegal construction as part of reforms.
The Egypt regime has targeted journalists in an ongoing crackdown on dissent since the 2013 military ouster of Islamist president Mohamed Morsi.
The clampdown has swept up thousands of Islamist supporters of the late Morsi as well as secular activists, lawyers and academics.
Egypt ranks 166th out of 180 countries in media watchdog Reporters Without Borders’ 2020 world press freedom index.