An Egyptian court on Tuesday quashed a government decision to hand over two Red Sea islands to Saudi Arabia, judicial sources said, overruling a deal that had sparked public outrage.
President Abdel Fattah al-Sisi announced the controversial accord in April during a visit to Cairo by Saudi King Salman.
A judge told AFP that the decision by the State Council -- Egypt's highest administrative court -- "cancels the signing" of the deal, which put two islands in the Straits of Tiran under Riyadh's control.
The handover prompted an outcry from many Egyptians, and sparked protests against Sisi.
A court last month sentenced 51 people to two years in jail for taking part in protests against the accord, which police quickly dispersed.
In the lead-up to the protests, police already made dozens of arrests to discourage a repeat of a large rally on April 15 at which demonstrators chanted for the "fall of the regime".
Egypt's appeals court in May overturned five-year jail terms for 47 people convicted of taking part in non-authorised protests, but upheld fines of more than $11,000 each.
Tuesday's ruling on the islands deal is not final and may be challenged by the government.
Lawyer Khaled Ali, who brought the case, told AFP the court's verdict "shows that the two territories are Egyptian... and cannot be given away".
Saudi Arabia is one of Sisi's main regional backers, and the kingdom has provided Egypt with billions of dollars worth of aid and investment since the former army chief took power.
Cairo says the islands had always belonged to Saudi Arabia and that Egypt had merely administered them while on lease since the 1950s.
Critics accuse Sisi of "selling" the islands in return for Saudi investments.