Seven people have been killed in Cairo in overnight clashes between security forces and supporters of Egypt's ousted President Mohammed Morsi, BBC News reported.

Police used tear gas to drive back protesters, some hurling rocks, who had blocked a main road in the capital. The clashes came as a senior US envoy visited Egypt, saying it had been given a "second chance" at democracy.

William Burns met interim leaders but was snubbed by rival groups, including Morsi's Muslim Brotherhood.

Morsi was ousted on 3 July in what many have said was a military coup. The army says it was fulfilling the demands of the people after mass anti-Morsi protests.

Monday July 15 battles erupted after hundreds of angry protesters blocked the 6 October bridge, a major arterial route.

Police fired tear gas to try to break up the blockade, and protesters responded by throwing stones. Other clashes broke out in the Giza district, at the south-west end.

The head of Egypt's emergency services, Mohamed Sultan, said two people had died on or around the bridge and five in Giza.

State media said 261 people were injured in the clashes, which lasted into the early hours of Tuesday. Sultan said security personnel were among the casualties.