Egyptian President Abdel Fattah Al-Sisi condemned the deadly attack targeted St Mark’s Cathedral in Cairo and declared three days of national mourning.

In a statement, President Sisi promised justice and said that the terrorism facing Egypt targets the whole nation – Muslims and Christians – and that Egypt will not be shaken by it.

The attack, which occurred at around 10AM local time, killed at least 23 people and injured many others.

An official funeral will be held tomorrow in Cairo, with a number of high level officials attending. According to a government source, President Sisi will also attend the funeral.

Hundreds of protesters have been prevented by police from entering the Coptic Cathedral in Cairo hours after the deadly explosion.

According to state media Al-Ahram, the protesters had gathered outside the Cathedral condemning the attack and calling for justice.

Tensions are reportedly high, with many of the protesters urging police to let them enter the Cathedral to pray for the dead.

The attack, one of the deadliest to take place in Egypt’s capital city in recent years, targeted a chapel connected to St Mark’s Cathedral, the main Coptic Christian church in Egypt. The explosion, reportedly caused by a bomb planted inside, resulted in the deaths of mostly women Copts.

Following the explosion, a number of senior officials visited the scene. Egypt’s Prime Minister, Prosecutor-General, and Minister of Religious Endowments are among some of the high level officials who have visited the scene and condemned the attack.

Meanwhile, Egypt’s Al-Azhar, the top Islamic authority in the country, condemned the attack in a statement released immediately after the attack. Egypt has cancelled all celebrations marking the Prophet’s Birthday, which takes place this year on 11 December.

Egypt has faced a number of terror attacks since the ouster of former President Mohammed Morsi in July 2013. However, the majority of attacks have occurred in North Sinai, where a war against militancy has been waged by local tribes and Egypt’s military.