A man screams beside a bus carrying Coptic Christians which came under attack outside Cairo. Picture: Egypt’s Coptic Orthodox Church via AP

Cairo - Unknown gunmen on Friday attacked a bus carrying Coptic Christians to a desert monastery in southern Egypt, killing seven people, police said.

The attack took place near St Samuel Monastery in the southern province of Minya and also injured seven, a security source added in a statement carried by state Egyptian television.

When attacked, the bus was driving along a side road to the monastery because the main road was closed after earlier security orders due to its desert location and lack of phone communication, it added.

The search for the attackers was ongoing, the source said, without details. So far, no one has claimed responsibility for the attack.

Initially, a spokesman for the Coptic Church, Boulis Halim, said that at least seven were killed and 14 injured in the attack.

In May 2017, 29 people were killed in a similar attack in Minya.

Friday's assault comes a day before President Abdel-Fattah al-Sissi opens a major world youth forum in the Sinai resort town of Sharm al-Sheikh, which authorities hope will showcase security in the area.

In recent years, the northern part of the Sinai Peninsula has seen deadly militant attacks, mainly against security forces.

Egypt has witnessed a spate of militant attacks since 2013, when the army deposed Islamist president Mohammad Morsi, the country's first democratically elected leader, after mass protests against his rule.

Several of the attacks have targeted Christians and churches.

In April 2017, twin suicide bombings, claimed by Islamic State, targeted two Coptic churches, killing 48 people. The Palm Sunday bombings prompted Egypt to declare a nationwide state of emergency.

Christians account for around 10 per cent of Egypt's predominantly Muslim population of about 100 million.