Egyptian authorities have deployed troops and armored vehicles to the city of Suez following violence between security forces and protesters that has left at least seven people dead and hundreds wounded.
Six people were reported killed in Suez, and another was reported killed in Ismailia.
Officials said more than 450 people were injured as clashes broke out across the country on January 25, the second anniversary of the 2011 uprising that toppled longtime ruler Hosni Mubarak.
Officials said the army had been deployed to Suez to protect government institutions.
In a message on Twitter, President Muhammad Morsi has called for calm, saying citizens should respect the ideals of the revolution and express their views peacefully.
He blamed the violence on "criminals" and vowed to bring wrongdoers to justice.
Protesters accuse Morsi of failing to fulfill the democratic goals of the revolution and of surrendering the country’s development to the Muslim Brotherhood, from which Morsi hails.
Unrest was reported in 12 of Egypt’s 27 provinces. Clashes occurred outside the presidential palace in Cairo, in the second city of Alexandria, and other cities and towns.
Reports say protesters in some areas targeted Muslim Brotherhood offices and government buildings.
In Suez, live ammunition was reported to have been fired, and police have used tear gas to repel protesters in several cities.
The unrest marks the latest confrontation between protesters and the government of Morsi, who was elected in a democratic poll at the end of June to become Egypt’s first Islamist-backed president.
Protesters are seeking the cancelation or amendment of the new constitution, which was passed in a controversial referendum in December.
The charter, drafted by a council dominated by Islamists, has been criticized for failing to guarantee basic democratic rights and freedoms for women and members of minority groups.
There is also significant personal hostility among protesters toward Morsi. The president triggered mass protests in November and December after he issued a series of decrees that temporarily gave him near-absolute powers, including over the judiciary.
The Muslim Brotherhood and other supporters of the president have sought to portray the opposition as trying to use undemocratic means to reverse the results of democratic processes.
The unrest comes with many Egyptians frustrated over a continuing economic downturn.
The turmoil of the past two years has severely damaged the economy of the world’s 15th-most-populous country, with foreign direct business investment, tourism, and foreign-currency reserves all declining sharply.
With reporting by Reuters, AP, and AFP