Egyptian security forces fired tear gas Friday at demonstrators protesting President Abdel-Fattah al-Sisi's decision to hand over two Red Sea islands to Saudi Arabia. Chants of "leave, leave!" directed at al-Sisi marked the first significant wave of street protests since the former army chief became president in 2014.Riot police first cracked down on protesters in Cairo's twin city of Giza, where demonstrators had gathered at two prominent mosques after Friday prayers and started marching toward Tahrir Square downtown. Many carried signs reading, "Land is Honor" and denouncing the surrender of the islands. Others chanted, "The people want the fall of the regime" and "Down with military rule!"After police fired tear gas, the protesters ran in all directions, according to videos posted online by activists. Several photojournalists covering the protests were briefly detained near al-Istiqama mosque in Giza, according to witnesses at the scene who spoke on condition of anonymity because they feared for their own safety.All unauthorized demonstrations in Egypt are illegal and security forces have, in the past, used lethal force against peaceful demonstrators.Egypt's state news agency quoted an unnamed official as saying that the protesters were members of the banned Muslim Brotherhood group and that they chanted "anti-regime slogans." The official said police responded with tear gas after protesters threw rocks at them.Another demonstration of nearly 2000 protesters gathered outside the Press Syndicate downtown, a few meters from a collection of armored vehicles and hundreds of police in full riot gear who sealed off the surrounding streets. The protesters there chanted, "They sold our lands to the Saudis." Except for a handful of bearded men and female protesters wearing full-face veils, there was little sign of an organized Brotherhood presence among the demonstrators."If we give up the lands now, there will be more future concessions for him to stay in power, for few more months," said Alaa Morsi, one of the protesters, echoing a widely-held notion that al-Sisi essentially sold Egyptian territory in exchange for much-needed Saudi financial support, to shore up his rule.What infuriated many was the secretive nature of the deal and particularly its timing. It was announced at the same time the Saudis were pledging billions of dollars of loans, causing critics and even some former al-Sisi supporters to accuse the president of a desperate and humiliating territorial sell-off."He should have told us before the deal," said 28-year-old lawyer and protester Rania Rafaat, who was carrying a banner read, "al-Sisi sold his land, leave."Al-Sisi has defended his decision on the islands and tried to defuse the controversy.The government maintains that the islands of Tiran and Sanafir at the mouth of the Gulf of Aqaba belong to Saudi Arabia, which asked Egypt in 1950 to protect them from Israel. Israel captured the islands in the 1967 Middle East war, but handed them back to Egypt under their 1979 peace treaty.In response, Egyptians have taken to social networking sites including Facebook and Twitter, posting numerous old maps to prove Egypt's ownership of the islands.Though relatively small in number, the protests come at a time of public tension and tight security, underscoring increasing public discontent at al-Sisi's rule since he was elected president in the summer of 2014.