PORT SAID, Egypt (AP) -- Port Said residents were burying their dead Sunday in mass funerals that could erupt into another wave of violent protests, a day after rioting in the Egyptian coastal city left at least 37 dead and hundreds wounded.
Army troops backed by armored vehicles staked out positions at key government facilities to protect state interests and try to restore order as hundreds of mourners gathered at the city's main mosque to offer prayers for the dead.
On Saturday, angry residents went on a rampage through Port Said after a court handed down death sentences to almost two dozen local fans involved in a deadly melee at a soccer game last year. The rioters attacked the prison where the defendants were being held and tried to storm police stations and government offices around the city.
The street clashes in Port Said were the latest in a bout of unrest across the country that has left a total of 48 people dead since Friday. That death toll includes 11 people killed in clashes between police and protesters marking the second anniversary of the uprising that overthrew longtime leader Hosni Mubarak.
On Sunday, clashes continued for the fourth successive day between protesters and police near Cairo's central Tahrir square, birthplace of the 2011 uprising. Police used tear gas, while the protesters pelted them with rocks.
The bloodshed highlights the challenges facing Islamist President Mohammed Morsi, who took office nearly seven months ago following the revolt that ousted Mubarak. Critics say Morsi has failed to carry out promised reforms in the country's judiciary and police force, and claim little has improved in the two years since the uprising.
At the heart of the rising opposition toward Morsi's rule is a newly adopted constitution, which was adopted in a nationwide referendum.
Critics say the document has an Islamist slant and was drafted by the president's allies without the participation of liberals and Christians. They are calling for the formation of a national unity government, early presidential elections and amendments to disputed clauses in the constitution.
Morsi and the Muslim Brotherhood, the Islamist group from which he hails, counter that the opposition was seeking to overturn the results of democratic and free elections.
As the situation in Port Said spiraled out of control Saturday, police disappeared from the city's streets, residents and security officials said, staying put in their camps, police stations and the city's security headquarters.
The military then dispatched troops to the city, which is located on the northern tip of the Suez Canal. Soldiers took up positions at vital state facilities, including the local power and water stations, the city's main courthouse, the local government building and the city prison. Navy sailors were guarding the local offices of the Suez Canal company.
Navy vessels were escorting merchant ships sailing through the international waterway, and army helicopters were flying over the canal to ensure the safety of shipping, according to Suez Canal spokesman Tareq Hassanein.
Residents said Port Said was quiet overnight except for intermittent bursts of gunfire. The city was still on edge early Sunday -- streets were largely deserted, stores were closed for the second successive day, and some hotels asked guests to leave, fearing more violence.
Funerals for those killed Saturday were taking place Sunday at the city's landmark Mariam Mosque, and residents said they expected more street clashes afterward.
The officials and residents spoke on condition of anonymity because they were not authorized to speak to the media.
Saturday's riot in Port Said mostly stemmed from animosity between police and die-hard soccer fans know as Ultras, who also were part of the uprising that toppled Mubarak's regime.
The Ultras were at the forefront of protests against the military generals who took over from Mubarak and are now again on the frontlines of protests against the rule of Islamist President Mohammed Morsi.
Survivors and witnesses of the Feb. 1 soccer melee in Port Said say Mubarak loyalists had a hand in instigating the killings, which began after Port Said's home team Al-Masry beat Cairo's Al-Ahly 3-1. Some say "hired thugs" wearing green T-shirts posing as Al-Masry fans led the attacks.
Others say, at the very least, police were responsible for gross negligence in the soccer violence, which killed 74 people, most of them Al-Ahly fans.
Anger at police was evident in Port Said, home to most of the 73 men accused of involvement in the bloodshed, although the trial was held outside Cairo.
Judge Sobhi Abdel-Maguid did not give his reasoning when he handed down the sentences for 21 defendants on Saturday. Executions in Egypt are usually carried out by hanging.
Verdicts for the remaining 52 defendants, including nine security officials, are scheduled to be delivered March 9. Some have been charged with murder and others with assisting the attackers. All the defendants -- who were not present in the courtroom Saturday for security reasons -- can appeal the verdict.