Three people have been killed after unknown gunmen opened fire during a wedding ceremony outside a Coptic church in a Cairo suburb, increasing tension in the Egyptian capital.

The victims included an eight-year-old girl and the groom's mother. At least nine people were injured in the attack which took place in northern Cairo's al-Warak neighbourhood.

"There were two men on a motorbike and one of them opened fire," an interior ministry spokesperson said. The assailants shot randomly at people, said witnesses.

No group has claimed responsibility for the attack. Security forces have been deployed around the church shortly after the incident.

"We heard a very loud sound as if something was collapsing. I found a woman seated in a chair with lots of bullet wounds, covered in blood. Many other people had fallen around her, including a child," said an eyewitness quoted by the BBC.

Some of the Islamist groups, which support deposed president Mohamed Morsi, blame the Church for his overthrow. The Christian community, which makes up 10 percent of the Egyptian population, is largely Coptic and has been frequently targeted since Morsi's removal in July 2013.

The attacks on churches have reached a new peak since the 14 August crackdown, when security forces opened fire on Islamist protest camps killing hundreds of protesters.

Meanwhile, in a separate development, Egyptian security forces have fired tear gas on student protesters who attempted to march in Cairo.

The 3,000 Islamist students from the al-Azhar university hurled rocks at the riot police and verbally abused them, said the interior ministry.

"Security forces tried for almost half an hour to lure them into opening the road, but they insisted on their position," said the ministry's statement. Around a dozen students are said to have been arrested by the police.

Egypt's interim administration has come down heavily on members of Morsi's Muslim Brotherhood, which has been officially outlawed by the judiciary.