Suspected militants on Monday ambushed two mini-buses carrying off-duty policemen in Egypt's northern Sinai Peninsula, killing 25 of them execution-style and wounding two, security officials said.

The killings, which took place near the border town of Rafah, compound Egypt's woes a day after police fired tear gas to free a prison guard from rioting detainees, killing at least 36. The deaths of the 36 detainees and the 25 policemen take to nearly 1,000 the number of people killed in Egypt since Wednesday's simultaneous assaults on two sit-in protest camps by supporters of ousted Islamist President Mohammed Morsi.

In Monday's attack in Sinai, the militants forced the two vehicles to stop, ordered the policemen out and forced them to lie on the ground before they shot them to death, the officials said. The policemen were in civilian clothes, said the officials, speaking on condition of anonymity because they were not authorized to talk to the media.

The deaths Sunday of the prisoners, who were captured during clashes the past couple of days around Cairo's central Ramses Square, came as military chief Gen. Abdel-Fatah el-Sissi vowed the military would stand firm in the face of the rising violence but also called for the inclusion of Islamists in the post-Morsi political process.

There was initial confusion over how the Sinai ambush had happened, and the officials at first said the policemen were killed when the militants fired rocket-propelled grenades at the two minibuses carrying the men. Such confusion over details in the immediate aftermath of attacks is common. Egyptian state television also reported that the men were killed execution-style.

Sinai, a strategic region bordering the Gaza Strip and Israel, has been witnessing almost daily attacks since Morsi's July 3 ouster in a military coup, Military and security forces have been engaged in a long-running battle against militants in the northern half of the peninsula. Militants and tribesmen have used the area for smuggling and other criminal activity for years and have on occasion fired rockets into Israel and staged cross-border attacks.

The detainees killed on Sunday were in a prison truck convoy of some 600 prisoners heading to Abu Zaabal prison in northern Egypt, security officials told The Associated Press. Detainees in one of the trucks rioted and managed to capture a police officer inside, the officials said.

Security forces fired tear gas into the truck in hopes of freeing the badly beaten officer, the officials said. The officials said those killed died from suffocating from the gas. Those officials also spoke on condition of anonymity because they were not authorized to speak to journalists.

However, the officials' version of event contradicted reports about the incident carried by state media. The official website of state television reported that the deaths took place after security forces clashed with militants near the prison and detainees came under fire while trying to escape. The official MENA state news agency also said the trucks came under attack from gunmen.

State media also said the people killed and the gunmen belonged to the Muslim Brotherhood, the Islamist organization that Morsi hails from. The officials who spoke to AP said some of the detainees belonged to the Brotherhood, while others didn't. The differences in the accounts could not be immediately reconciled.

The violence added to the ever-rising death toll in days of unrest.

Egypt's military-backed interim government declared a state of emergency after Wednesday's crackdown on the pro-Morsi sit-ins in Cairo and ensuing street clashes elsewhere in the capital and in other cities and towns across the country.

A curfew was also imposed, turning the capital of over 18 million people into a ghost town after 7 p.m. every night. The military-backed interim government that took over after Morsi's ouster has also began taking harsher measures to cripple the Brotherhood.

Security forces arrested hundreds of Muslim Brotherhood members early Sunday in raids on their homes in different cities, aimed at disrupting planned rallies to support Morsi. The Cabinet also held an emergency meeting to consider banning the group.

A possible ban - which authorities say would be implemented over the group's use of violence - would be a repeat of the decades-long struggle between the state and the Brotherhood. It also would drain the group's financial resources and allow for mass arrests of its members. That likely would diminish the chances of a negotiated solution to the crisis and push the group again underground.

The Brotherhood has shown no signs of backing down though.

Under the banner of an anti-coup alliance, the group held protests Sunday, though many appeared smaller in scale than others held in recent days. In the coastal city of Alexandria, protesters clashed with residents. In the southern city of Assiut, security forces fired tear gas to disperse hundreds rallying in front of a mosque.

"They think they can end the movement," said Muslim Brotherhood senior member Saad Emara. "The more killings, the more people join us."

However, the government blames Islamists for series of attacks on churches and police stations, increasing public anger against the group.

In his first appearance since the violence began, el-Sissi spoke at length in an hour-long speech about the motives behind ousting Morsi. The general said the Islamist president exploited democracy to monopolize power. He again said the military's action "protected Egyptians from civil war," despite the ongoing violence on the streets.

"We will not stand by silently watching the destruction of the country and the people or the torching the nation and terrorizing the citizens," el-Sissi said in a speech aired on state television. "I am not threatening anyone - If the goal is to destroy the country and the people, no!"

The general said that the military didn't seek power but instead "have the honor to protect the people's will - which is much dearer (than) ruling Egypt."