Update 4.08pm: At least 28 people have died and another 22 were injured after masked militants opened fire on a bus packed with Coptic Christians, including children, south of the Egyptian capital.
Earlier: At least 26 people have died and another 25 were wounded after masked gunmen opened fire on a bus carrying Coptic Christians south of the Egyptian capital.
The assault happened in the Minya area, about 140 miles south of Cairo, while the bus was travelling to Saint Samuel the Confessor Monastery in Maghagha.
No group has immediately claimed responsibility for the attack, which came on the eve of the Muslim holy month of Ramadan.
Witnesses said there were eight to 10 attackers dressed in military uniforms and wearing masks. The victims had been travelling from the nearby province of Bani Suief to visit the monastery.
Health ministry spokesman Khaled Mogahed said the death toll reached 26 but feared it could rise further. According to the Copts United news portal, only three children survived the attack.
Arab TV stations showed images of a damaged bus along a roadside, many of its windows shattered. Ambulances were parked around it as bodies lay on the ground, covered with black plastic sheets.
Though no-one has claimed responsibility for the attack as yet, it had all the hallmarks of Egypt's Islamic State (IS) affiliate.
Egypt has been fighting militants linked to IS who have waged an insurgency, mainly focused on the volatile north of the Sinai Peninsula, although there have also been attacks on the mainland.
Friday's attack is the third against Christians in Egypt in six months. In April, twin suicide bombings struck two churches on Palm Sunday, and in December, a suicide bombing targeted a Cairo church. The attacks left more than 75 dead and scores wounded. IS has claimed responsibility for these attacks and vowed to carry out more.
Late last month, Pope Francis visited Egypt in part to show his support for the Christians of this Muslim majority Arab nation.
During the trip, Francis paid tribute to the victims of the December bombing at Cairo's St Peter's church, which is located in close proximity to St Mark's cathedral, the seat of the Coptic Orthodox Church.
Following the Pope's visit, the IS affiliate in Egypt vowed to escalate attacks against Christians, urging Muslims to steer clear of Christian gatherings and western embassies as they are targets of their group's militants.
Egypt's Copts, the Middle East's largest Christian community, have repeatedly complained of suffering discrimination, as well as outright attacks, at hands of the country's majority Muslim population.
Over the past decades, they have been the immediate targets of Islamic extremists.
They rallied behind general-turned-president, Abdel-Fattah el-Sissi, in 2013 when he ousted his Islamist predecessor Mohammed Morsi, who hails from the Muslim Brotherhood group.
Attacks on Christian homes, businesses and churches subsequently surged, especially in the country's south.