CAIRO/PORT SAID: Protesters wearing surgical masks, scarves and hoods clashed with police wielding tear gas as violence in the Egyptian city of Port Said entered its fifth day Thursday.

The city at the northern end of the Suez Canal has been a flashpoint since January, with violent protests erupting over death sentences given to residents in connection with a football stadium riot in which more than 70 people died last year.

Security has deteriorated in Egypt since the overthrow of President Hosni Mubarak in a popular uprising two years ago, with some of the worst unrest in Port Said, an industrial city where residents complain of being marginalized.

Youths threw stones and made lewd gestures at a line of police officers who released smoke bombs into streets strewn with

rubbish, television footage from pan-Arab channel Al-Arabiya showed.

At least six people have been killed in this week’s protests in the Mediterranean city, including three policemen.

The security services in the city told Reuters they were ramping up protection of the central prison and Suez Canal offices before a court hearing Saturday, which is expected to confirm the death sentence for 21 prisoners.

The clashes Thursday prevented some of the staff of a Suez Canal container company from going to work.

Underlining the overwhelming task facing authorities trying to restore order, police strikes spread across Egypt, with thousands of low-ranking officers protesting what they claim is the politicization of the force in favor of the Muslim Brotherhood.

The strike is a rare show of defiance by policemen against their superiors and threatens to unravel a security force already weakened by two years of post-Mubarak unrest.

For decades, Egypt’s police force aggressively targeted the Brotherhood and other Islamist groups that were once outlawed.

Policemen say they are now being forced to confront protesters angry with Mursi, and his Brotherhood supporters.

They also are angry that they can be tried in military courts and complain that current laws do not protect them when they

carry out their duties.

The Interior Ministry said in a statement Thursday that it stood at equal distance from all parties and that the ministry was being objective in its duties.

The ministry, which oversees police in Egypt, relies on low-ranking policemen to protect government buildings, particularly in the face of angry protests in Suez Canal cities and in areas north of Cairo in the Nile Delta region.

Hundreds of policemen have been wounded in the past six weeks of unrest in those areas, and several have been killed in the anti-government protests.

In Cairo, dozens of policemen blocked the entrance to one of the city’s main police stations and expressed anger at Mursi’s policies. Others held a sit-in outside Mursi’s house in his hometown of Zagazig, northeast of the capital.

South of the capital, in Assiut and Luxor, policemen protested what they say is new Interior Minister Mohammad Ibrahim’s attempts to use the force to protect the Brotherhood.

Security officials in the Interior Ministry said that the former interior minister refused orders to direct police against anti-Mursi protesters outside the presidential palace in Cairo in December. They said the Brotherhood was also enraged that police did not protect the group’s offices that month from being torched by Egyptians angry at Mursi’s handling of the drafting of the constitution.

The strike comes just two days before a court is expected to hand down verdicts to defendants standing trial for a deadly football riot that killed 74 people in Port Said. Nine security officials are among the 73 people on trial.

Anger is also boiling in the Nile Delta province of Dakahliya, where protesters and policemen accuse the new security director there of ordering heavy-handed tactics to suppress anti-Brotherhood protests.

Sami al-Meehy was appointed the province’s security chief in recent days, just as anger there was mounting against the Brotherhood and a civil disobedience campaign began. Police there are accused of intentionally running over and killing a protester last weekend.

The police force, a frightening and powerful underpinning of Mubarak’s rule, has been accused by rights activists of carrying out the same brutal tactics under Mursi.

Egypt’s uprising, which began two years ago on a day meant to commemorate police, was largely rooted in widespread hatred of security forces under Mubarak. More than 100 policemen have been put on trial for the killings of protesters, and all

but two were acquitted.

Allegations of torture at the hands of police persist, and more than 70 people have been killed in nationwide protests since late January. Rights groups allege that police are still operating with impunity.

Lawlessness also has plagued parts of Egypt’s Sinai Peninsula, where Bedouin gunmen seized and briefly held the country boss of U.S. oil major ExxonMobil and his wife Thursday.

Exxon said Andy Wills, chairman and managing director of its Egypt and Cyprus operations, and his wife were both unhurt.

The British couple were seized when they stopped to change money in Ras es-Sidr, 150 km southeast of Cairo, while driving to a Sinai beach resort, Egyptian security sources said. The couple were held for several hours before being handed over to the army after negotiations with tribal elders.