President Abdel-Fattah el-Sisi insisted on the need for stability in the Arab world’s most populous country.

Egypt’s president urged citizens to defend the state and its institutions from the “forces of evil” on Sunday, a day before planned demonstrations against his policies, including the transfer of two Red Sea islands to Saudi Arabia.

In a widely televised speech, Abdel-Fattah el-Sisi insisted on the need for stability in the Arab world’s most populous country, saying that attempts to degrade it “won’t be successful” if Egypt stands united.

“We must protect these institutions because these mean the state,” he said. “I am reiterating to the Egyptian people this is the responsibility of all of us, for us to protect this security and stability.”

Earlier this month, thousands marched against Sisi’s policies in the largest demonstrations since he assumed office in 2014.

The protesters, including politicians and activists, called for more demonstrations on Monday, a national holiday that commemorates the withdrawal of the last Israeli troops from the Sinai Peninsula in 1982 under the Camp David peace agreement.

The armed forces will deploy at vital sites Monday to prevent saboteurs from taking advantage of these protests, Egypt’s military spokesman Brig. Gen. Mohammed Samir said Sunday.

Sisi’s comments raise the possibility of large-scale counter-demonstrations that could turn violent, in addition to a potentially harsh police crackdown — especially if the demonstrators attempt to reach the heavily policed Tahrir Square.

Protests are essentially banned in Egypt under laws passed after el-Sissi led the military overthrow of his elected but divisive Islamist predecessor, Mohammed Mursi, in 2013.

A petition titled “Egypt is not for sale,” which calls for a reversal of the decision on the islands and supports the protests, was signed by more than 300 Egyptian novelists, lawyers and activists, and several calls have been made on social media for Monday’s demonstrations to converge on Tahrir Square, the epicenter of the 2011 revolt against Mubarak.

The Muslim Brotherhood said in a Sunday statement it supports the protests and is calling on people to join them.

Since Friday, security troops have been out in force, with armored personnel carriers stationed at key traffic areas, while security agents have rounded up dozens of activists, journalists, and lawyers from their homes and cafes in downtown Cairo.

Two Interior Ministry spokesmen did not respond to repeated telephone calls seeking comment.

Also Sunday, Interior Minister Magdy Abdel-Ghaffar met with officials to review preparations to confront any attempts to “break the law,” the ministry said in a statement. It quoted Abdel-Ghaffar as saying that the security apparatus would be ready to address any action that could disturb public security with “the utmost firmness and decisiveness,” urging citizens to ignore calls to create chaos and drive a wedge between the people and police.

The protests earlier this month were pegged to anger over Sisi’s decision to transfer sovereignty of the two islands to Saudi Arabia in a deal concluded in secret and announced during a visit by Saudi King Salman.

Many infuriated Egyptians accused the government of trading land for aid and investment from the kingdom. The government insists the two islands, Tiran and Sanafir, always belonged to Saudi Arabia but were placed under Egyptian protection in 1950 because Riyadh feared they would be attacked by Israel.

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