WASHINGTON (AFP) - US Secretary of State John Kerry expressed "deep concern" Saturday about the "bloodshed and violence" in Egypt that has killed and injured scores, saying the country faced a "pivotal moment."

Mr Kerry, in a statement following calls with Egyptian and EU officials, also urged an "independent and impartial inquiry" into the events of the past 24 hours and urged all of the Egypt's leaders to act to "help their country take a step back from the brink."

At least 65 people were killed during clashes in Cairo early Saturday, Egypt's health ministry said, after violence erupted at a demonstration in support of ousted president Mohamed Mursi.

The ministry said nine others died in violence in Egypt's second city Alexandria, putting the toll in two days of unrest at 74.

"This is a pivotal moment for Egypt," Mr Kerry said.

"Over two years ago, a revolution began. Its final verdict is not yet decided, but it will be forever impacted by what happens right now."

Mr Kerry also said that, at a time of extreme volatility, Egyptian authorities have "a moral and legal obligation to respect the right of peaceful assembly and freedom of expression."

"Violence not only further sets back the process of reconciliation and democratisation in Egypt, but it will negatively impact regional stability," he said.

"At this critical juncture, it is essential that the security forces and the interim government respect the right of peaceful protest, including the ongoing sit-in demonstrations."

Mr Kerry said he conveyed his concern in telephone calls to Interim Vice-President Mohamed ElBaradei, Interim Foreign Minister Nabil Fahmy, and European Union High Representative Catherine Ashton.