The brutality of Egypt’s once-feared security state helped spark Egypt’s 2011 revolution. Now those security forces are swinging back into action, and this time they are being hailed as heroes by many of the secular activists and liberals who once campaigned against them.

The reversal started when police in crisp white uniforms joined the successful effort to oust President Mohamed Morsi four weeks ago, drawing cheers from crowds. Since then, police officers who were chased off the streets after the 2011 revolution have been back in force. Meanwhile, the interim government has restored the mandate of the domestic counterterrorism agency to scrutinize religious and “extremist” activity. Those powers were stripped after the revolution because they were widely interpreted as justifying the torture of Islamists and other government opponents.

The Muslim Brotherhood, which backs Morsi, called on its supporters Monday to protest the revived power of the security forces by demonstrating in front of Interior Ministry offices around the country, raising fears of further violence after police and their plainclothes allies killed at least 80 Morsi supporters Saturday.

Egyptian authorities detained two leaders of the moderate Islamist al-Wasat party on Monday, in an apparent broadening of a crackdown on Islamist political activity. The arrests occurred even as the Obama administration condemned the violence and called for Catherine Ashton, a top European Union official visiting Cairo, to be granted access to Morsi. He has been held incommunicado since the Egyptian army deposed him on July 3.

In a striking sign of the widening split in Egyptian society, many of the liberal and secular groups that revolted in 2011 are welcoming the resurrection of the forces they had once joined the Islamists in condemning.

Some of the secularists said they were worn out from more than two years of rising crime, and feared a burgeoning insurgency in Egypt’s Sinai Peninsula, which they said justifies the revitalization of the counterterrorism force.

“It’s a reconciliation,” said Ehab Samir, a top official of the Free Egyptians Party, a secular political party that supported Morsi’s ouster. “You can’t stay at odds with them. Your security is dependent on having a strong police force.”

The possibility of a vastly expanded security state initially appeared to unsettle Tamarod, or Rebel, the movement that organized the June protests leading to Morsi’s exit. Last weekend, the group said on its Web site that “there is no way to accept the return of [former president Hosni] Mubarak’s State Security.”

But by Monday, the criticism had softened.

“We appreciate the burden on the Interior Ministry and the state, because they are facing an 80-year-old organization” — the Muslim Brotherhood — “that is ready to drag the country into a civil war,” Mohamed Abdel-Aziz, a Tamarod spokesman, said in an interview.

The Muslim Brotherhood has said it simply wants the return of the democratically elected president.

Some human rights activists say that security forces were never fully reined in during Morsi’s year-long rule but that police and national security had stopped targeting Islamists, who had been one of their major targets.

Still, the plan to reestablish the old powers of the security forces is a “significant shift,” said Heba Morayef, Egypt director for Human Rights Watch,

“It goes beyond the Islamist-secular divide to something much bigger,” she said. “I don’t like using the word ‘counterrevolution,’ but the police feel they’ve been vindicated, and they have been able to use the last few months to put themselves in a position of power again.”

In 2011, the police and state security forces defended Mubarak, the long-ruling autocrat, and the military ultimately did not. Many of the investigations in the aftermath of the 18-day uprising focused on police violence against revolutionaries. Police officers known for their swagger under Mubarak became a subdued presence on the streets, declining even to enforce traffic laws. The top leadership of State Security was dismissed, and the force was given a new name, National Security.

But on Saturday, Interior Minister Mohamed Ibrahim suggested that the reshuffle might have been a mistake.

“You cannot have security in a country without political security,” Ibrahim said at a news conference, blaming some of Egypt’s turmoil on the abolition of departments in the domestic counterterrorism agency that monitored religious and extremist groups. Ibrahim said he was reinstating some officers who had been dismissed and had “started rebuilding” the departments.

He said that he would soon move to clear away large Muslim Brotherhood-led sit-ins that have been taking place in Cairo since Morsi’s departure.

The Obama administration on Monday urged Egypt’s interim leaders to refrain from using violence. It again declined to label the removal of Morsi a “coup,” a characterization that could force a halt to the $1.5 billion that the United States sends Egypt every year, much of it military aid.

“The United States strongly condemns the bloodshed and violence in Cairo and Alexandria over the weekend,” White House deputy spokesman Josh Earnest said. “Egyptian authorities have a moral and legal obligation to respect the right of peaceful assembly and freedom of expression.”

Inside the vast, fortified state security headquarters, which was burned and ransacked by protesters in the chaotic weeks after Mubarak was forced from power in February 2011, security officers said Monday that they welcomed the changed attitudes. Human rights groups and critics have said that some of the Mubarak era’s worst torture took place inside the compound.

In a drab, windowless reception room inside the compound, three security officers in plainclothes said that they had simply been misunderstood after the revolution.

“People say that this place is only for torture,” one officer said. “This is not going to be a place of torture. We are here just to collect information and to combat terrorism. That’s it.”

Sharaf al-Hourani contributed to this report.