Egyptian officials say gunmen have attacked a pipeline once used to supply gas to Israel – the fifth assault on the facility in the Sinai region since February.

A state-run media report says masked men launched rocket-propelled grenades at the al-Shulaq natural gas terminal on Saturday. It says the pipe was hit but the line contained no gas and had not been operating for some time.

The attack took place a day after at least four people were killed in clashes between an armed group and Egyptian security forces in the Sinai region.

Egyptian officials say the unrest started on Friday when at least 100 armed men rode into the town of el-Arish and tried to storm a police station.

A state-run media report says an army officer and three civilians were killed during the incident and at least 19 others were injured. It says security forces have arrested four suspects.

Authorities have not identified the attackers but witnesses say some waved flags with Islamic slogans as they fired shots into the air.