FILE - In this Wednesday, Feb. 2, 2011 file photo, A supporter of President Hosni Mubarak, on camel, fights with anti-Mubarak protesters in Cairo, Egypt. More Arabs are politically engaged than ever before,... (Associated Press) 
 
 Egyptian opposition protesters are gathering in Cairo's Tahrir Square to mark the second anniversary of the uprising that toppled Hosni Mubarak's autocratic regime. 
 
 The protesters, mostly led by liberals and secularists, are using the anniversary to stage a show of strength in a bid to force President Mohammed Morsi to amend a disputed constitution drafted by his Islamist allies. They are also demanding freedom of expression and the independence of the judiciary. 
 
 Hundreds of thousands are expected to turn out for the rallies planned in Cairo and several major cities. Morsi's Muslim Brotherhood and other Islamist groups are staying off the streets to avoid clashes. 
 
 Friday's rallies come a day after opposition protesters battled police for hours near Tahrir. The clashes injured scores of opposition protesters. ||||| Associated Press Supporters of President Hosni Mubarak, bottom, clash Wednesday with opponents, top, in Cairo's Tahrir Square, the scene of recent protests that shook the Egyptian regime. 
 
 Violence erupted in Egypt's capital when supporters of President Hosni Mubarak clashed for the first time with protesters, as the regime dug in against demands, from within the country and from Washington, that a transfer of power begin immediately. 
 
 The clashes began hours after Mr. Mubarak announced in a speech late Tuesday that he wouldn't run in elections slated for later this year. They gained intensity during the day in central Cairo's Tahrir Square, with the two sides rushing at each other, wielding clubs and throwing Molotov cocktails. Some Mubarak supporters charged protesters on horseback and camelback, a tactic the regime has employed against past demonstrations. Clutches of soldiers looked on, doing little to intervene. 
 
 The Obama administration, watching the violence, began pushing harder for Mr. Mubarak to quickly step aside and make way for a transitional government, people familiar with the matter said. 
 
 The U.S. began to chart a course of reforms and, for the first time since large-scale protests erupted in Egypt more than a week ago, made it clear that Washington and Cairo—close allies for three decades—are now on different tracks. 
 
 An interim government, made up of opposition parties and elements of the current regime, could buy time to rewrite the Egyptian constitution, allow opposition parties to organize, and lay the groundwork for elections later this year, say supporters of the idea. 
 
 Washington's stance pitted the U.S. against Mr. Mubarak, who has indicated he would stick around until after elections, and against those among the Egyptian opposition who are pushing for much speedier elections. 
 
 Egypt's Strongman View Interactive Take a look back at Egyptian President Hosni Mubarak's career. 
 
 Egypt's Foreign Ministry, underscoring the sense that the regime was trying to regain the upper hand, rejected President Barack Obama's call for an immediate start to a political transition. The ministry said "foreign parties" aimed to "incite the internal situation in Egypt." 
 
 But White House Press Secretary Robert Gibbs, said when the White House says change is needed now, "'now' means yesterday." 
 
 Leading opposition figures also dug in, repeating their rejection of Mr. Mubarak's offer to step down after negotiating political reforms and holding elections, which have been scheduled for September. "Once he's out of the country" the demonstrators will go home, opposition leader Mohamed ElBaradei said in an interview. 
 
 Opposition leaders hadn't previously called for Mr. Mubarak's departure from the country; other officials in Mr. ElBaradei's alliance said on Wednesday that Mr. Mubarak could remain in Egypt as a normal citizen if he gave up power. 
 
 More than 600 people were wounded and three died in Wednesday's clashes, according to the Health Ministry. 
 
 Clashes were continuing to flare into the early hours of Thursday morning, as fires continued to burn around Tahrir Square. Pro-regime demonstrators blockaded off the northern part of the square with tanks and burned trucks. Molotov cocktails, thrown from a bridge nearby where pro-Mubarak protesters had assembled, set a building on fire. On Thursday morning, protest organizer Mustafa el-Naggar said he saw the bodies of three more dead protesters being carried toward an ambulance, according to the Associated Press. 
 
 Journal Photos: Clashes in Cairo View Slideshow Guy Martin for The Wall Street Journal Anti-government protesters clashed with supporters of Egyptian President Hosni Mubarak in Tahrir Square. Photos: Wednesday Protests View Slideshow Lefteris Pitarakis/Associated Press Pro-government demonstrators, bottom, watched as cars burned during clashes with anti-government demonstrators, top, behind barriers, in Tahrir Square. Regional Upheaval View Interactive A succession of rallies and demonstrations, in Egypt, Jordan, Yemen and Algeria have been inspired directly by the popular outpouring of anger that toppled Tunisian President Zine al-Abidine Ben Ali. See how these uprising progressed. 
 
 The dueling rhetoric and the street fighting appeared to be leading toward another large showdown on Friday, when opposition figures vowed to call another rally. 
 
 The turmoil in Egypt continued to fan tensions across the region. In Jordan, where weeks of protests convinced King Abdullah II to dismiss the government and name a new prime minister on Tuesday, the Muslim Brotherhood political organization publicly rejected his new choice and demanded yet another. 
 
 In Israel, which has relations with only Jordan and Egypt in the Arab world, Prime Minister Benjamin Netanyahu said the situation in Egypt could affect Israel's security for years to come. 
 
 Many foreign companies operating in Egypt continued to cut back on operations. 
 
 Procter & Gamble Co., for example, said its two Egypt plants remained closed, and the foreign national employees it evacuated over the past few days haven't returned to Egypt. 
 
 The government restored Internet service Wednesday, having cut off almost all service to deprive protesters of an organizing tool. 
 
 But the counterattack on behalf of the regime extended to social networks such as Facebook and email messages—the mediums antiregime demonstrators used so effectively in the early stages of the protests more than a week ago. 
 
 "Please spread the word to your relatives, colleagues and friends. Mubarak's speech was enough," read one message posted on a Facebook site. "He deserves to leave his position in a respectable way, as much as we deserve a safe, secured and stable Country....Don't 4get that we have a real enemies waiting Egypt to fall:( SAVE THE COUNTRY NOW!!!" 
 
 It was unclear where such messages were coming from. 
 
 The mobilization of government backers began almost immediately after Mr. Mubarak's speech late Tuesday. Crowds of government backers soon began showing up amid antigovernment protesters in the northern city of Alexandria. 
 
 In Cairo, by midday Wednesday, thousands of regime supporters marched on Tahrir Square, pushing out roughly equal numbers of antiregime demonstrators camped there. 
 
 Bloody scenes of street battles were common. Pro- and anti-Mubarak groups faced off, chanting slogans at each other, fighting and hurling missiles. 
 
 Protesters at two entrances to Tahrir Square came under attack from men heaving rocks and running into the protesters with horses and camels. 
 
 Other regime supporters came armed with metal rods, which they wielded against protesters. 
 
 At the downtown entrance to the square, groups of Mubarak supporters started organizing charges, running up and down the street. Protesters responded by forming a human barrier three to four people deep. 
 
 Mohamed Abdu, a 22-year-old graduate of Helwan University and a member of the Muslim Brotherhood, grew visibly shaken as the men began hurling rocks over the human barricade. One man on the protesters' side pulled out a pair of large light bulbs from his backpack and threw them at the Mubarak supporters. He was quickly shouted down by protesters chanting "peace." 
 
 As the sun set, gunshots could be heard near the square; a tree and building adjacent to the renowned Egyptian Museum caught on fire. 
 
 While the regime has been accused in the past of paying workers to attack antiregime protesters, many of the government backers interviewed on the streets Wednesday seemed sincere in expressing either undiluted support for Mr. Mubarak or a sense that demonstrations against him should now end. 
 
 Sayed Mohammed Sayed, a 37-year-old supporter of Mr. Mubarak, said the protesters pushed things too far by refusing to back down after the president agreed to pursue reforms and eventually step down. 
 
 "The situation is unacceptable," the air-conditioner technician said. "The majority of protesters are young people and aren't aware of their actions and consequences." 
 
 Ibrahim Saadouni, 47, a lawyer, said he believed the violence was started by the thugs for hire that are a standard feature of Egyptian electoral politics. "They've come to create a civil war," Mr. Saadouni said. "They're doing this to make war so the army will step in to end the demonstrations, because we won't leave." 
 
 Egyptian state-controlled television said that Muslim Brotherhood members were responsible for most of the violence in the square, including throwing incendiary devices—accusations the Muslim Brotherhood denied. 
 
 The Obama administration condemned attacks by pro-Mubarak forces. "We are deeply concerned about attacks on the media and peaceful demonstrators," Mr. Gibbs said. 
 
 —Adam Entous, Margaret Coker, Marc Champion, Tamer El-Ghobashy and Christopher Rhoads contributed to this article. 
 
 Write to Charles Levinson at charles.levinson@wsj.com, Summer Said at summer.said@dowjones.com and Jonathan Weisman at jonathan.weisman@wsj.com
– Two years after protests began in Cairo that would lead to the overthrow of Hosni Mubarak, protesters are once again gathering in Tahrir Square, reports the AP. Led by liberals and secularists, the protesters are now demonstrating against President Mohamed Morsi and the Muslim Brotherhood, which they accuse of threatening Egypt's young democracy. Hundreds of thousands are expected to march in protests across Egypt today. Police and protesters clashed yesterday and early this morning in Cairo, with demonstrators throwing Molotov cocktails and firecrackers and police responding with tear gas, reports Reuters. Egyptian officials said 25 people had been hurt since fighting flared yesterday. The Muslim Brotherhood says it will not stage counterprotests in order to avoid increasing the unrest.