Police officers in more than a third of Egyptian provinces have gone on strike, including in parts of Cairo and in Port Said, the troubled northern city where more than 50 people have died in the past month in clashes between police and protesters.

Police have also refused to protect President Mohamed Morsi's home in the Nile delta province of Sharqiya. Among several seemingly contradictory grievances, police demand better weapons. But conversely, they also claim the Morsi regime is using them as unwilling pawns in the suppression of protesters who demand the regime's downfall.

"They're trying to Ikhwanise the police and we are against that," claimed Ahab Kamel, a spokesman for an informal union of junior police officers, who was on strike in Port Said. Ikhwan is the Arabic word for Morsi's Muslim Brotherhood.

"We are at the same distance from all the political parties," added Kamel, sitting in the city's el-Sharq police station in civilian clothes, afraid to be seen in uniform by a local population furious with recent alleged police brutality.

The strike is the latest crack to emerge in the Egyptian state, which has been dogged by civil unrest in several cities over the past six weeks. It also adds a new dimension to the ongoing national debate about police abuses, which was a major cause of both the 2011 uprising that toppled Hosni Mubarak, and the current unrest that continued across several pockets of Egypt this weekend.

Campaigners claim that the police have resumed the use of torture, and in some cases, murder. A recent report by the United Group, a group of human rights lawyers, allege there have been at least 127 victims of police malpractice (pdf) since December

In one case, lawyers say a 28-year-old activist, Mohamed el-Guindy, was killed by police after officers took him to a police camp in January. He was allegedly strangled with a cord and electrocuted via his tongue. Authorities first claimed the activists died in a car crash – a claim later contradicted by an official medical report.

Campaigners and residents in Port Said have also documented multiple accounts of police firing indiscriminately at protesters.

But policemen on strike in Port Said deny the allegations. "I'm sure that this isn't the police," claimed Mohamed el-Adawy, deputy commander at el-Sharq police station, as he piled seven rifle rounds on his desk – for use as self-defence, he said. "It was thugs on the street."

Other officer argued that police were acting under extreme psychological pressure. "When people say that we are using force against the protesters, you have to go on the other side and see the situation when thousands are attacking you," said Kamel, who also claimed that the police had reformed their ways since the 2011 uprising.

But rights activists say that abuse continues. "There's definitely more activists subject to torture because there's more activism going on," said Aida Seif el-Dawla, the co-founder of the Egyptian Association Against Torture.

Tellingly, she reported that many of the recent survivors had been mocked by police in custody for their participation in overthrow of Mubarak. "The police want to belittle the revolution," she said.

Some striking policemen claim their treatment of protesters is a result of interference from Morsi and the Muslim Brotherhood. But the Brotherhood argues that it has little control over an intransigent institution, loyal to Mubarak holdovers, that will take years to reform.

"The corruption of the past 60 years is not going to be solved in just one or two or even five years," Walid al-Haddad, a spokesman for its political wing, the Freedom and Justice party, has told the Guardian. A small number of Islamist policemen also claim they have been discriminated against for wearing beards.

For their part, human rights activists feel that while Morsi may not have as much control over the police as officers claim, reforming the service is not one of his, or his colleagues', priorities. "They have a choice: to remain in power supported by the people. Or remain in power supported by institutions like the police," said Seif el-Dawla.

But this weekend, as police strikes spread across the country, even the second option seemed unlikely.

"I think we [can] safely say a police mutiny is underway in #Egypt," tweeted Issandr el-Amrani, an analyst and commentator on Egyptian politics.