CAIRO—The Egyptian military intervened Wednesday afternoon to quell the biggest riots since the country's former president fell in February, as new uprisings stymie the country's newly reformed civilian police force and threaten to delay the country's transition to democratic rule. As many as 5,000 protesters, many of them family members of those killed in Egypt's February uprising, overwhelmed the country's riot police Tuesday evening and Wednesday morning. More than 1,000 people suffered light injuries from rock-throwing and tear
gas, the Ministry of Health reported, but only 16 people remained hospitalized Wednesday afternoon. Police arrested 40 people, including an American and a British national, according to MENA, Egypt's official state news agency. The renewed violence, and the police's apparent inability to control Cairo's streets without military assistance, mark a significant setback for Egypt's provisional government, which had sought to re-establish internal security before guiding the country toward parliamentary elections scheduled for September. The abiding instability, along with paroxysms of sectarian violence over the past several months, come as several mostly secular political leaders say Egypt isn't ready to complete its transition to democracy November's scheduled presidential elections. Whether Egypt's police can offer adequate security for parliamentary elections is already a point of anxiety for the transitional government. In contrast with recent protests that had clear political aims, the past day's violence revived Egypt's police as a focus of public anger. Police brutality and corruption was a primary grievance of the protesters who toppled President Hosni Mubarak in February. Those protests reached a turning point when the police yielded control of the streets to Egypt's more-trusted military, before melting largely from sight. Since then, Egypt's Ministry of Interior has sought to earn public trust by reform from within as its forces have trickled back onto streets. The ministry oversees regular police as well as Egypt's Central Security Forces—a paramilitary law-enforcement agency normally tasked with riot control—and Homeland Security, the successor to Egypt's reviled State Security agency. Wael Abbas, an Egyptian blogger and pro-democracy activist, said the past day's events reveal that the stated reforms within these law-enforcement agencies have proven inadequate. "The Ministry of Interior as it is at the moment should be dissolved completely. It should be demilitarized," said Mr. Abbas, who was present at some of the recent protests. "It's the same Central Security using tear gas with peaceful protesters, rubber bullets, violence—the same as during Mubarak's time." Unlike in previous protests, few among those who convened on Tahrir Square appeared to be connected with the protest movement that ousted Mr. Mubarak. According to some witnesses, some appeared to be local youths spoiling for a fight. Accounts of the latest riots at times diverge. But common to most retellings, including a statement posted by the Ministry of Interior on its official Facebook page, is that family members of the "martyrs" killed by police officers earlier this year during the revolution gathered Tuesday evening at a theater in the Cairo suburb of Agouza for a ceremony that had been planned in their honor by a local organization. According to the ministry and some witnesses, police officers arrived to prevent nonrelatives from entering the theater. After scuffles broke out between the family members and police, the officers used hand-held weapons to subdue the crowd. The ministry blamed unidentified "thugs" for the attacks on the families. Family members then crossed the Nile River to demonstrate in front of the Ministry of Interior, the object of popular ire during the February uprising. Witnesses said officers from Egypt's Central Security Forces, a paramilitary law-enforcement agency normally tasked with riot control, threw rocks at the protesters, whose numbers had by then swelled to several thousand. By about 10 p.m. Tuesday, the protesters fled to nearby Tahrir Square,the focus of the protests during Egypt's revolution, and lobbed rocks at police for about 15 minutes before the riot police employed tear gas to disperse the crowds. Close-combat fighting raged in Tahrir Square until at least 3:00 a.m. and resumed again later on Wednesday before the military inserted themselves between protesters and police officers who were defending the ministry's outer walls. The rioting came two days after relatives of slain protesters attacked police outside a Cairo courthouse following a judge's decision to delay the trial of former interior minister Habib Al Adly, who is charged with ordering demonstrators' murders. Mustafa Shishtawy, 23, said he rushed to Tahrir Square on Tuesday night when he heard that the families of deceased protesters had been attacked by police. "It was a déjà vu of 28th of January," said Mr. Shishtawy, referring to the "Friday of Rage" in the early days of Egypt's revolution. "They threw too much tear gas on us," he said. "It was definitely revenge from the police because some of them were injured when we were throwing stones." Egypt's attorney general said Wednesday his office will investigate the Tahrir Square events. The violence forms the first major rebuke for Egypt's efforts to hastily reform its police after they abruptly disappeared during the uprising in late January. Since then, the military has handled the bulk of the day-to-day law enforcement while Egypt's vast security force tried to heal itself from within. "Any country that changes from a regime institution to a democratic institution has to pass through a liquid period like this," said Aasr Nigm Al Din, the head of training for Egypt's Homeland Security, which earlier this year replaced the State Security agency. The twin pressures to both reform and redeploy have been a major challenge for the police, an institution that many Egyptians had long considered corrupt beyond repair. Mr. Mubarak's regime had used the police as a means of preserving power rather than ensuring public safety, said Mr. Nigm Al Din. He and other officers have led the internal police reform effort over the past few months by focusing on holding officers accountable and depoliticizing police work. Tuesday and Wednesday's clashes in downtown Cairo were the police's first test against a large-scale demonstration without military support, and Mr. Nigm Al Din acknowledged that the violence will harm efforts by the interior ministry to gain public trust.