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Hundreds of Islamists loyal to deposed president Mohamed Morsi clashed with security forces as they rallied for his return, after a US envoy urged Egypt's army-backed leaders to end violence.
The demonstrators cut off the October 6 bridge across the Nile in the heart of Cairo, before the security forces fired tear gas to drive them back.
The pro-Morsi protesters, who had turned out in their thousands after the Ramadan iftar meal to demand his return, responded by hurling rocks at the security forces, who again dispersed them by firing tear gas.
The clashes, the first in the Egyptian capital since dozens of pro-Morsi demonstrators were shot dead outside an elite military headquarters a week ago, ended after about 10 minutes.
Hours earlier, Under Secretary of State Bill Burns urged the country's divided factions to engage in dialogue and end violence, on the first visit to Egypt by a senior US official since the military toppled Morsi in a popularly backed coup on July 3.
"The first priority must be to end violence and incitement, prevent retribution, and begin a serious and substantive dialogue among all sides and all political parties," Burns said.
He was speaking after meeting the general behind the coup, army chief Abdel Fattah al-Sisi, as well as the military-appointed president Adly Mansour and interim premier Hazem al-Beblawi.
Egypt's new leaders are pushing ahead with a transition plan for an interim government and fresh elections, but Morsi's Muslim Brotherhood defiantly insists on his reinstatement.
A State Department spokeswoman confirmed Burns did not meet with any Brotherhood officials, while Tamarod, the movement that spearheaded the grassroots campaign against Morsi, said it rejected an invitation to meet the US envoy.
"We rejected the invitation... Because the United States did not stand with the Egyptian people from the beginning," Islam Hammam, one of the group's organisers, told AFP.
Burns' brief visit comes as the authorities tighten the screws on Morsi's backers, freezing the assets of 14 top Islamists, and with Egypt rocked by a wave of deadly attacks, notably in the Sinai.
Three factory workers were killed in a rocket-propelled grenade attack in the restive peninsula, medics said.
Coptic Christians have also been killed in the Sinai, including a priest, as part of a what an Egyptian rights group said was a string of sectarian violence around the country since the Islamist president's overthrow.
