Muslim Brotherhood on streets only despite killings

Thousands of supporters of Egypt's Muslim Brotherhood stood their ground in Cairo on Sunday, saying they would not leave the streets despite "massacres" by security forces who shot dozens of them dead.

Egypt's ambulance service said 72 people were killed in Saturday's violence at a Cairo vigil by backers of deposed President Mohamed Mursi, triggering global anxiety that the Arab world's most populous country risked plunging into the abyss.

"They will not be content until they bring back everything from the era of the corrupt, murderous security and intelligence state," senior Brotherhood official Essam el-Erian said on Facebook. "They've stepped up their efforts to do so by committing massacres never before seen in Egyptian history."

The Interior Ministry has rejected eyewitness accounts that police opened fire on the crowds and a public prosecutor has launched a probe into the violence, investigating 72 suspects for an array of crimes including murder and blocking streets.

Although Cairo was quiet on Sunday, violent clashes rattled the Suez Canal city of Port Said, with a 17-year-old youth killed in fighting between the pro- and anti-Mursi camps and a further 29 people injured, security sources said.