An Egyptian military court has sentenced 11 Muslim Brotherhood members to life in prison for violence targeting the army in the port city of Suez last month.
Forty-five other Brotherhood members were handed five-year jail terms on Tuesday, and eight defendants were acquitted.
The men were accused of "shooting and adopting violent means" against the army in Suez on Aug. 14 following a military crackdown in the streets of Cairo against supporters of ousted President Mohamed Morsi, who was deposed on July 3. Morsi belonged to the Brotherhood movement.
The Brotherhood was founded in 1928 and formally dissolved by Egypt's army rulers in 1954. The Brotherhood operated for decades as a formally outlawed organization until veteran autocrat Hosni Mubarak was deposed in 2011.
The movement then won a series of elections culminating in last year's presidential vote. The military deposed Morsi after mass protests against his rule.
Since then, most of the Brotherhood's top leadership has been arrested and face charges of inciting violence. Morsi was himself referred to trial on Sunday on the same charge.
Earlier on Tuesday, Egyptian helicopters fired rockets at militants in the northern Sinai Peninsula, killing at least eight and injuring 15 others in an ongoing campaign to quell Islamic radicals who have escalated attacks in the largely lawless region since Morsi's ouster, Egypt's official news agency said.
Egyptian troops have stepped up their crackdown on militants in the peninsula bordering Gaza and Israel, arresting suspects and destroying tunnels along the Gaza border used for smuggling weapons and people.
Security officials told The Associated Press that military helicopters targeted numerous locations along the borders with Gaza and northern Sinai. The strikes were targeted at hideouts where militants were meeting in two villages, Touma and Moqataa, along with a car carrying suspects, according to the state news agency MENA.
A military official said the death toll was a bit higher, at 13, and told the AP the strikes also hit hideouts and vehicles in two other villages, Joura and Mahdiya.
One helicopter shot at a moving car, apparently killing the occupants, said another official. Two weapons caches were destroyed and three suspects running from airstrikes were arrested at a nearby checkpoint, he said.
Forces cordoned off the area to prevent militants from escaping as troops combed the villages, the officials said, speaking on condition of anonymity because he was not authorized to speak with the media.
Three houses were destroyed and part of a nearby mosque was damaged, a witness who spoke anonymously for fear of reprisal told AP.
Ali Hassan Khalaf, who lives just outside Moqataa, said he saw helicopters flying over targeted areas a day earlier, taking aerial images. He said the main family in the village has given militants a safe haven.
Army commandos late Monday arrested two members of an al-Qaeda-inspired group that fired rockets at Israel, according to another security official. Commandos stormed two houses in Joura, near Sheikh Zuweyid, and detained the two members of the Mujahideen Shura Council in the Environs of Jerusalem, he said.
The officials spoke anonymously because they were not authorized to talk with the media.
The two members of the group are also believed to have been involved in the killing of 25 police recruits last month near the border in one of the worst recent attacks against Egyptian security forces. The mastermind of the attack was arrested last week, and the two suspects detained Monday are accused of setting up and firing the rockets used in the attacks, the official said.
Security forces still have a long list of militants they are trying to arrest. Most are thought to be in hiding at the border area with Gaza and Israel and in the central Sinai mountains.