Thousands of Egyptian protesters angered by President Abdel Fattah al-Sisi's decision to hand over two islands to Saudi Arabia called on Friday for the downfall of the government, chanting a powerful slogan used in a 2011 uprising.

Sisi, who once enjoyed widespread support, has faced mounting criticism in recent months, including over his management of the economy.

"The people want the downfall of the regime," the protesters yelled outside the Cairo press syndicate, using the same phrase heard during the 2011 revolt against president Hosni Mubarak who later stepped down.

They also chanted: "Sisi Mubarak", "We don't want you, leave" and "We own the land and you are agents who sold our land.”

Sisi's government announced last week the signing of a maritime demarcation accord that put the uninhabited Red Sea islands of Tiran and Sanafir, which lie between Saudi Arabia and Egypt's Sinai Peninsula, in Saudi waters, prompting an outcry in Egyptian newspapers and on social media.

Saudi and Egyptian officials say the islands belong to the kingdom and were only under Egyptian control because Saudi Arabia had asked Cairo in 1950 to protect them.

Meanwhile, in other parts of Cairo, police fired tear gas at protesters, security sources said.

A Reuters witness said a crowd was dispersed and riot police had taken control of an area outside a mosque in the Mohandiseen district of the capital. Four people were arrested, the security sources said.

Tear gas was also fired in the Giza area outside Cairo, dispersing about 200 people, security sources said.

Critics say the government has mishandled a series of crises from an investigation into the torture and killing of an Italian student in Cairo to a bomb that brought down a Russian airliner in the Sinai last October.