Policemen stand beside the microbus which carried Coptic Christians when gunmen opened fire in Menyia, Egypt, Nov. 2, 2018.
Some Christians in Minya said Saturday's attack proves not enough is being done to protect Egypt's Christians.
Gunmen killed at least seven Coptic Christians in Egypt as they were traveling on a bus near a monastery - the most serious assault on the religious minority in over a year.
ISIS militants have for years been fighting security forces in the Sinai Peninsula and along Egypt's porous desert border with Libya.
"I mourn with great sorrow the victims who fell today at the traitorous hands that seek to undermine the nation's fabric", Egyptian President Abdel Fattah al-Sissi said of Friday'a attack.
The province of Minya has become known for anti-Christian violence and questions are being asked of Egyptian authorities as to why the route taken by the bus had not been secured.
Locals said the minibuses were part of a convoy of three carrying pilgrims from the remote desert monastery. More than 100 Copts have been killed in such attacks since 2011, according to The Associated Press news agency.
Sisi also reportedly called the Coptic Pope Tawadros II to offer his condolences and led a minute's silence at a youth forum.
Church spokesman Bouls Halim said the death toll in Friday's attack was expected to rise.
Egypt is a Muslim-majority country and its Christian minority - mostly members of the Coptic Orthodox Church - make up around 10% of the population.
"Today's attack on a bus of Coptic Christian pilgrims in Minya, Egypt has again exacted a toll of civilian deaths and injured", the spokesperson said, adding that "the attack was a stark reminder of the security challenges that Egypt is facing", stated Maja Kocijancic, European Union's Spokesperson for Foreign Affairs and Security Policy/European Neighbourhood Policy and Enlargement Negotiations.
The Interior Ministry said police were pursuing the attackers, who fled the scene. It is also the latest by IS to target Christians in churches in Cairo, the Mediterranean city of Alexandria and Tanta in the Nile Delta north of the capital.
This follows attacks on dozens of churches, homes and businesses belonging to Copts after the bloody breaking up of two pro-Morsi gatherings in Cairo in August and with perceptions that Copts had backed his overthrow. They have long complained of persecution and insufficient protection.
The US State Department condemned the attack in a statement Friday.