Four Christians have been killed in an attack on a church as a wedding was taking place in the city of Giza in Egypt.

Christian Solidarity Worldwide reports that the dead were all guests at the wedding and include the mother of the groom, Camilia Attiya, 56, and two children, eight-year-old Mariam Ashraf and 12-year-old Miriam Nabil. The other victim was 45-year-old Samir Fahmy.

They were killed when masked gunman opened fire as wedding guests were leaving the Coptic Orthodox Church of the Virgin Mary in Warraq al-Hadar, Giza, on Sunday.

The gunman was riding a motorcycle at the time and fired indiscriminately before driving away from the scene.

Sources confirmed to Christian Solidarity Worldwide that 18 people were injured in the attack.

According to Father Thomas Daoud Ibrahim, priest of the Warraq church, three wedding services had been taking place at the time of the attack.

Although no group has claimed responsibility for the attack, there has been a wave of violence against the Coptic community following the ousting of President Mohamed Morsi.

Copts have been victims of attacks by Muslim Brotherhood supporters who accuse them of colluding in Morsi's removal.  Senior members of the Muslim Brotherhood have also called for retribution against Copts.

The Muslim Brotherhood, Al-Gamaa Al-Islamiya and the Salafi Nour Party are among the Islamist groups that have condemned the attack and denied any involvement.

Prime Minister Hazem el-Beblawi said the attack was a "cowardly criminal act", while Al-Azhar Grand Imam Sheikh Ahmed el-Tayeb called it "a criminal attack against religion and morals".

Mervyn Thomas, Chief Executive of Christian Solidarity Worldwide said: "While the expressions of condolences from all sectors of Egyptian society are encouraging, we continue to urge adequate and timely protection for the Coptic community and Coptic gatherings in order to prevent such tragedies from occurring.

"Moreover, the culture of hate speech and impunity in which such attacks occur must also be addressed in order to ensure the emergence of a society in which all Egyptians can flourish, regardless of their religion or political affiliation."