Egyptian security officials say militants have attacked a mosque in the volatile Sinai Peninsula, leaving dozens of casualties.

The three police officers say the extremists attacked the al-Rawdah mosque in the town of Bir al-Abd, 40 km (25 miles) from the North Sinai provincial capital of el-Arish.

They say men in four off-road vehicles opened fire on worshipers during Friday prayers.

Victims are being transferred to local hospitals, they added, speaking on condition of anonymity because they weren't authorized to brief reporters.