Egypt's army chief said political strife was pushing the state to the brink of collapse - a stark warning from the institution that ran the country until last year, as Cairo's first elected leader struggles to contain bloody street violence.
General Abdel Fattah al-Sisi, appointed by President Mohamed Mursi last year to head the military, added in a statement on Tuesday that one of the primary goals of deploying troops in cities on the Suez Canal was to protect the waterway that is vital for Egypt's economy and world trade.
Sisi's comments, published on an official army Facebook page, followed 52 deaths in the past week of disorder and highlighted the mounting sense of crisis facing Egypt and its Islamist head of state who is struggling to fix a teetering economy and needs to prepare Egypt for a parliamentary election in a few months that is meant to cement the new democracy.
The comments are unlikely to mean the army wants to take back the power it held, in effect, for six decades since the end of the colonial period and in the interim period after the overthrow of former general Hosni Mubarak two years ago.
But it sends a powerful message that the Egypt's biggest institution, with a huge economic as well as security role and a recipient of massive direct U.S. subsidies, is worried about the fate of the nation after five days of turmoil in major cities.
"The continuation of the struggle of the different political forces... over the management of state affairs could lead to the collapse of the state," said General Abdel Fattah al-Sisi, who is also defence minister in the government Mursi appointed.
He said the economic, political and social challenges facing the country represented "a real threat to the security of Egypt and the cohesiveness of the Egyptian state" and the army would remain "the solid and cohesive block" on which the state rests.
Sisi was appointed by Mursi after the army handed over power to the new president in June. Mursi sacked Field Marshal Hussein Tantawi, who had been in charge of Egypt during the transition and who had also been Mubarak's defence minister for 20 years.
Political opponents spurned a call by Mursi for talks on Monday to try to end the violence. Instead, huge crowds of protesters took to the streets in Cairo and Alexandria, and in the three Suez Canal cities - Port Said, Ismailia and Suez - where Mursi on Sunday imposed emergency rule and a curfew.
'Down, Down, Mursi'
Residents in the three canal cities demonstrated overnight in defiance of the curfew. At least two men died in fighting in Port Said, raising to at least 42 people who have now been killed there, most of them by gunshot wounds.
Protests first flared to mark the second anniversary of the uprising that erupted on Jan. 25, 2011 and toppled Mubarak 18 days later. They have been exacerbated by riots in Port Said by residents enraged by a court ruling sentencing several people from the city to death over deadly soccer violence last year.
"Down, down with Mohamed Mursi! Down, down with the state of emergency!" crowds shouted in Ismailia. In Cairo, flames lit up the night sky as protesters set vehicles ablaze.
The demonstrators accuse Mursi of betraying the two-year-old revolution. Mursi and his supporters in the Muslim Brotherhood accuse the protesters of seeking to overthrow Egypt's first ever democratically elected leader by undemocratic means.
Debris from days of unrest was strewn on the streets around Cairo's Tahrir Square, cauldron of the anti-Mubarak uprising.
Youths clambered over a burned-out police van. But unlike on previous mornings in the past few days, there was no early sign of renewed clashes with police.
Since the 2011 revolt, Islamists who Mubarak spent his 30-year rule suppressing have won two referendums, two parliamentary elections and a presidential vote.
But that legitimacy has been challenged by an opposition that accuses Mursi of imposing a new form of authoritarianism, and punctuated by repeated waves of unrest that have prevented a return to stability in the most populous Arab state.
The army has already been deployed in Port Said and Suez and the government agreed a measure to let soldiers arrest civilians as part of the state of emergency.
The instability has provoked unease in Western capitals, where officials worry about the direction of a powerful regional player that has a peace deal with Israel. The United States condemned the bloodshed and called on Egyptian leaders to make clear violence is not acceptable..
Mursi's invitation to rivals to hold a national dialogue with Islamists on Monday was spurned by the main opposition National Salvation Front coalition, which described it as "cosmetic".
The only liberal politician who attended, Ayman Nour, told Egypt's al-Hayat channel after the meeting ended late on Monday that attendees agreed to meet again in a week.
He said Mursi had promised to look at changes to the constitution requested by the opposition but did not consider the opposition's request for a government of national unity. Mursi's pushing through last month of a new constitution which critics see as too Islamic remains a bone of contention.
The president announced the emergency measures on television on Sunday. "The protection of the nation is the responsibility of everyone. We will confront any threat to its security with force and firmness within the remit of the law," Mursi said.
His demeanour infuriated his opponents, not least when he wagged a finger, imperiously, at the camera.
Some activists said Mursi's measures to try to impose control on the turbulent streets could backfire.
"Martial law, state of emergency and army arrests of civilians are not a solution to the crisis," said Ahmed Maher of the April 6 movement that helped galvanize the 2011 uprising. "All this will do is further provoke the youth. The solution has to be a political one that addresses the roots of the problem."