Cairo: Gunmen in a drive-by shooting killed three Egyptian policemen and wounded nine during an overnight rally by Islamist students in the capital, Cairo, authorities said on Tuesday.

The attack raises security concerns ahead of presidential elections next week, a vote the country’s retired army chief, Abdul Fattah Al Sissi, is widely expected to win. Al Sissi led the military when it ousted Islamist President Mohammad Mursi last July.

The Interior Ministry said about 250 students from the religious Al Azhar University took to the streets late on Monday night to show their support for Mursi, who hails from the Muslim Brotherhood group.

As riot police tried to quell the demonstration, three gunmen in a speeding car opened fire from behind the policemen, killing three and wounding nine, then fled from the scene, the ministry said.

No one immediately claimed responsibility for the attack but two Al Qaida-inspired groups, one based in Sinai, have carried out scores of similar attacks on military and police targets in recent months.

The Al Azhar University is a hotbed for Brotherhood students, who have been rioting almost daily, both inside the campus and in the surrounding streets, since Mursi was deposed last summer. The university has dismissed more than 70 students for taking part in rallies that turned violent and destroyed furniture and equipment on the campus.

Meanwhile, the state Mena news agency said suspected militants blew up a natural gas pipeline in the restive Sinai Peninsula late on Monday.

The report said the explosion, which took place south of the provincial capital of Al Arish, sparked a fire but that all valves were immediately closed to stop the flow of gas. The pipeline carries natural gas to an industrial area in central Sinai and also to Jordan.

Militant strikes on pipelines in Sinai have proliferated in recent years. The gas pipeline has been hit over 20 times since the 2011 uprising that toppled autocrat Hosni Mubarak in an uprising that was followed by a security vacuum.

The Al Qaida-inspired group, Ansar Beit Al Maqdis, based in the peninsula, has claimed responsibility for most of those bombings.