Twitter and Facebook users in Egypt with more than 5,000 followers will be monitored under the state's media regulator as part new laws tightening free speech and cracking down on dissent.
Egypt's parliament passed a bill regulating the press that includes restrictions on social media, one of the few remaining forums for critcisim in the increasingly authoritarian country.
The bill allows the government-appointed Supreme Media Council to monitor and take action against bloggers and Twitter and Facebook users with more than 5,000 followers who publish "fake news or incitement to illegal actions, violence or hate".
Violations may be punished by blocking the website, the law says, among other "appropriate actions".
Several prominent bloggers and activists with a large following on social media had been arrested over the past year, with the government showing little tolerance for dissent as it presses ahead with harsh economic reforms praised by international investors but criticised by many Egyptians for raising prices.
Several countries, including Britain, have laws against incitement on social media. But in Egypt laws banning incitement have been used to target dissidents for criticising the state or calling for protests.
The country has already blocked hundreds of websites, including local media like the independent Mada Masr and rights groups like Human Rights Watch.
Conventional media in the country, both state owned and private, is largely supportive of President Abdel Fattah al-Sisi who says Egypt enjoys a free press, yet has called on journalists to be careful in what they report.
"The law comes as a conclusion to the recent era of restrictions on free speech," said Khaled El-Balshy, an Egyptian editor and former Journalists' Syndicate official.
The bill was one of several adopted by the largely pro-Sisi legislature on Monday. Another grants immunity to military officers for actions following the army's overthrow of Islamist president Mohamed Morsi in 2013.
Hundreds of Islamist protesters were shot dead in clashes with security forces in the months after Mr Morsi was toppled by the army, then headed by Mr Sisi.
Mr Sisi, who won an election in March with 97 per cent of the vote against a sole candidate who expressed support for him, had been hailed as a hero by millions of Egyptians who had protested against Mr Morsi demanding the divisive Islamist's resignation.
He has since been criticised for leading an extensive crackdown on dissent.