There was no immediate claim of responsibility for the attack.
The attackers struck close to Saint Samuel the Confessor monastery in Minya, 260 kilometres up the River Nile from Cairo, Archbishop of Minya Anba Makarious told Reuters.
A similar attack took place in May 2017, when gunmen fired at a bus carrying Christians to the same monastery, killing at least 28 people.
Egypt's President Abdel-Fattah El-Sisi issued a statement on his official Facebook page shortly after the attack mourning the victims, vowing to continue the war against terrorism.
Egypt is a Muslim-majority country and its Christian minority - mostly members of the Coptic Orthodox Church - make up around 10% of the population.
EN IMÁGENES. Heidi Klum opta por "Shrek" para Halloween 2018
Algunas celebridades se han adelantado a la fecha mostrando los disfraces que han lucido en fiestas días antes de Halloween . La exmodelo ha dado algunas pistas en su cuenta oficial de Instagram .
Church spokesman Bouls Halim said the death toll in Friday's attack south of the capital Cairo was likely to rise.
A year earlier, a suicide bomber killed nearly 30 worshipers at a church in Cairo located in the Saint Mark's Cathedral complex, the seat of the Coptic papacy.
The jihadists also have killed hundreds of soldiers and police officers in Egypt in recent years and were allegedly behind a November 2017 attack against a Sinai mosque that killed more than 300 people.
Coptic Christians have been repeatedly targeted by terrorists.
Egypt says fighting Islamist militants is a priority to restore security after the years of turmoil that followed the Arab Spring protests in 2011.