At least 11 people have been killed after a gunman on a motorcycle opened fire on worshippers at a Coptic Christian church in Cairo.

Key points: The attack took place at a church in Cairo's south

The attack took place at a church in Cairo's south It's the latest in a series of terrorist assaults on Copts

It's the latest in a series of terrorist assaults on Copts Security has been ramped up ahead of Orthodox Christmas celebrations

Egypt's Interior Ministry said the Friday attack began when the gunman tried to break through the security cordon outside the Coptic Church of Mar Mina.

Two people were killed in a shop before the gunman opened fire on the church, killing at least nine people, and tried to throw an explosive device.

One of those killed was a police officer.

It was not clear how many assailants were involved. Egypt's Interior Ministry referred to only one, but the Coptic church mentioned "gunmen".

Earlier reports by security sources and state media said at least two attackers were involved, and that one was shot dead and another fled the scene.

The Interior Ministry did not explain the reason for the different accounts.

The church was being guarded by police in the run-up to Orthodox Christmas celebrations next week, security sources said.

Witnesses describe how the attack unfolded

Samir Gerges, a witness to Friday's church attack, said people inside the church closed the gates when the shooting began but that some bullets penetrated the building.

Mr Gerges said he was walking along a nearby street when the gunfire broke out. He saw people running and some taking cover in a nearby restaurant.

Another witness, 40-year-old Raouth Atta, was praying inside the church when the violence broke out.

"People were terrified and wanted to check on their families in other buildings of the church," she said.

"We stayed inside for 30 minutes before we were able to get out."

Once she was able to leave, Ms Atta said, she saw blood everywhere.

"We kept praying," said the Reverend Boules, who was teaching a class in the church complex. On hearing gunfire, he went to check on his students, who were panicking and terrified.

A video circulating on social media after the attack apparently showed the gunman lying on the ground with his face covered in blood.

Islamic State claims responsibility for latest attack on Copts

The local affiliate of the Islamic State group claimed responsibility for the attack in a statement carried by its Amaq propaganda wing, saying it was carried out by a "security detail" and that one of its men was "martyred" in the strike.

US President Donald Trump called Egyptian President Abdel Fattah al-Sisi and condemned the attack, the White House said in a statement.

The Interior Ministry said forces had "immediately dealt with the [attacker] and arrested him after he was wounded."

It added, "legal measures have been taken," without elaborating.

The general prosecutor said in a statement that an investigation has been launched into the incident.

Coptic Christians, also known as Copts, are the largest ethno-religious minority in Egypt, and make up roughly 10 per cent of the country's population.

Copts have been targeted by Islamic militants in a series of attacks that have left more than 100 people dead and scores wounded since December 2016.

Police have stepped up security measures around churches ahead of Coptic Christmas celebrations on January 7, deploying officers outside Christian places of worship and setting up metal detectors at some of the bigger churches.

Two assailants have attacked the Mar Mina Church in the Helwan district of southern Cairo. ( Reuters: Amr Abdallah Dalsh )

AP/Reuters