At least 23 Christian worshippers have died in an attack on a bus in Minya
A group of more than 50 Coptic Christians travelling towards the monastery of St Samuel near Minya, about 150 miles from Cairo, was targeted by "armed terrorists", according to state media.
So far least 26 people are reported to have been killed and a further 26 wounded.
Images brioadcast on state television show a coach riddled with bullets with almost every window smashed.
Bishop Anba Ermia, president of the Coptic Orthodox Cultural Centre, tweeted that as many as 35 people had died, including children.
Eyewitnesses said the Copts were attacked as they were going to pray at the monastery, in the western part of the province.
Their convoy was stopped on a road approaching the place of worship by a group of masked gunmen, who then opened fire.
An ambulance outside the monastery of St Samuel after at least 26 people were shot dead
Minya's provincial governor, Essam al-Bedaiwy, said the group had been travelling in two buses and truck when the attack happened, Reuters reported.
A spokesperson for Egypt's Interior Ministry said the gunmen were travelling in three vehicles.
President Abdel Fattah al-Sisi has called a meeting of security officials in the wake of the latest attack on the Coptic Orthodox Church – Egypt's largest Christian church and the Middle East's biggest Christian community.
Dozens of checkpoints and have been set up and police are patrolling the area as the hunt for the perpetrators begins.
The killings have been condemned by Muslim leaders.
Get Quotes on Home Insurance
Ahmed al-Tayeb, the grand imam of al-Azhar, Egypt's 1,000-year-old centre of Islamic learning, called for all Egyptians to "unite in the face of this brutal terrorism".
The Grand Mufti of Egypt, Shawki Allam, condemned the killers as "traitors".
Minya is home to a sizable Christian minority.
Christians make up around 10 per cent of Egypt's 92 million population and have repeatedly been targeted by Islamic extremists.
The Copts were attacked on the way to a monastery in Minya province
It is the latest fatal attack on Copts in Egypt in the past few months, after more than 45 people were killed in a double suicide bombing in April, when terrorists attacked churches in Tanta and Alexandria on Palm Sunday.
Another 25 people, mainly women and children, were killed in December when a bomb exploded outside the main Coptic Christian cathedral in Cairo.
ISIS claimed responsibility for the bombings, and warned more attacks would follow.
Although no group has yet claimed responsibility for the latest atrocity, the US Embassy & Consulate in Egypt yesterday warned of a a possible terrorist attack threatened by the Hassm group, a splinter cell of the Muslim Brotherhood.