Supporters of Egypt's former president, Mohamed Morsi, and residents backing government security forces have clashed in Cairo and Alexandria, leaving at least two people killed, according to a security official.

A large crowd of students, believed to be Morsi supporters, gathered at the gates of Al-Azhar University in Cairo on Friday, shouting and throwing projectiles at security forces.

Two armoured vehicles were deployed to the scene and police fired tear gas at demonstrators.One police officer sustained a head injury in the clashes.

At least 12 people were arrested during the clashes. It was not clear whether the deaths and arrests occurred in Cairo or Alexandria.

The clashes came just hours after two suicide bombers attacked a checkpoint and a nearby bus outside the south Sinai provincial capital of al-Tur, security officials said.

A police officer was killed and at least seven civilians were injured in the bombings.

Egypt has been hit by a series of violent assaults since Morsi was ousted in July of last year.

The violence first escalated in Sinai, where several al-Qaeda-inspired groups have long operated, but it has since moved into the Nile Delta and the country's capital, Cairo.

Fighters said that the attacks were a means of retaliating against violent crackdowns that have killed hundreds of Morsi supporters and led to the arrests of thousands more.

Friday's violence came just one day before the start of campaigning for Egypt's presidential election, which is scheduled to take place between May 26 and 27.

Source: Agencies