Gunmen attacked and killed at least eight police officers in a Cairo suburb, officials announced in the early hours of Sunday.

The officers were all travelling in a police vehicle in Helwan, just south of the capital, when the assault occurred.

The Interior Ministry says four gunmen with automatic weapons jumped out of a pickup truck, sprayed the police vehicle with bullets and then fled.

Witnesses claim the assailants wore masks.

A local affiliate of the extremist group "Islamic State" has claimed responsibility for the attack, in an online statement, according the Associated Press.

Egypt is in the grips of an insurgency that has killed hundreds of military personnel and police over the past three years.

The violence began in mid-2013 after then-army chief Abdel-Fattah el-Sisi toppled Islamist President Mohammed Morsi, amid protests against his rule.

Most of the militants' deadly attacks occur in the northern Sinai Peninsula, but rebels have also hit security forces and planted bombs in Cairo and other cities beyond the Sinai.

Meanwhile, there were chaotic scenes in two Egyptian courthouses on Saturday. In one of the cases, three journalists were sentenced to death.

Jazeera slams verdict

Two Al Jazeera journalists - news producer Alaa Omar Mohammed and news editor Ibrahim Mohammed Hilal - and fellow scribe Asmaa al-Khateib were all sentenced in absentia, and all are outside of Egypt. But the decision is not final.

The Grand Mufti, Egypt's top religious authority, is expected to review the case by June 18, but his decision is not binding either.

The Al Jazeera media network "rejects the absurd allegations that they (Mohammed and Hilal) were in collaboration with the elected government of Mohammed Morsi," a spokesman for Al-Jazeera said.

'Truth for Regeni'

In another hearing, an aid-worker who was helping the family of a slain Italian doctoral student had his detention extended, nearly two weeks after being arrested at his home.

Ahmed Abdullah, accused of inciting revolt and terrorism, heads the Egyptian Commission for Rights and Freedoms, a nongovernmental organization (NGO).

Abdullah's NGO had offered to assist the lawyers of the family of Giulio Regeni, the Italian doctoral student. Regeni disappeared on January 25, and his body, bearing all the signs of severe torture, was eventually found by the side of a road outside of Cairo.

From the cage in the courtroom, Abdullah said, "I will continue to fight for justice for Giulio." Upon entering the courthouse, Abdullah had carried a small origami, which read "Truth for Regeni" in Arabic.

bik/rc (Reuters, dpa, AP)