Egyptian President Abdel Fattah al - Sisi has signed a new law that tightens controls over the internet.
The legislation on "cybercrime" means websites can be blocked in Egypt if deemed to constitute a threat to national security or the economy, the BBC reported.
Anyone found guilty of running, or just visiting, such sites could face prison or a fine.
Authorities said on Saturday that the new measures are needed to tackle instability and terrorism.
The Cairo - based Association of Freedom of Thought and Expression said more than 500 websites had already been blocked in Egypt prior to the new law being signed.
Last month another bill was passed by parliament, yet to be approved by President Sisi, that would allow any social media accounts with more than 5, 000 followers to be placed under supervision.