Egypt blocked several media websites on Wednesday including those belonging to the Qatari Al-Jazeera news channel and an opposition television station based in Turkey, a security official said.
Mada Masr, an independent Egyptian media outlet that has published investigative reports on corruption, was also inaccessible on Wednesday night.
Egypt has accused Jazeera of supporting the outlawed Muslim Brotherhood movement it blames for violence after the military ousted them from power in 2013.
HuffPost Arabi, the Arabic website for the US outlet The Huffington Post, was also apparently blocked. The website had published articles critical of Egyptian government.
The website for Al-Sharq, a pro-Brotherhood channel based in Turkey, was also blocked.
The security official said 21 websites had been blocked but did not name them all.