A bomb has exploded in a church north of Cairo that was packed with Palm Sunday worshippers, killing at least 21 people and wounding as many as 38 others.

The attack took place on the Coptic Christian Palm Sunday, when the church in the Nile Delta town of Tanta was packed with worshippers, Egypt's Health Ministry said.

Ministry spokesman Khaled Megahed confirmed the toll from the attack in an interview with CBC TV.

Spokesman for Egypt's Ministry of Foreign Affairs Ahmed Abu Zeid said the incident was terror-related.

"Terrorism hits Egypt again, this time on Palm Sunday. Another obnoxious but failed attempt against all Egyptians," he tweeted.

Magdi Awad, the head of the provincial ambulance service, confirmed the toll.

No one immediately claimed the attack, which came just weeks before Pope Francis was due to visit Egypt.

A local Islamic State affiliate claimed a suicide bombing at a church in Cairo in December that killed around 30 people, mostly women, as well as a string of killings in the restive Sinai Peninsula that caused hundreds of Christians to flee to safer areas of the country.

A militant group called Liwa al-Thawra claimed responsibility for an April 1 bomb attack targeting a police training centre in Tanta, which wounded 16 people.

The group, believed to be linked to the outlawed Muslim Brotherhood, has mainly targeted security forces and distanced itself from attacks on Christians.

Egypt has struggled to combat a wave of Islamic militancy since the 2013 military overthrow of an elected Islamist president.

The attack was the latest in a series of assaults on Egypt's Christian minority, which makes up around 10 per cent of the population and has been repeatedly targeted by Islamic extremists.

More to come

Reuters, AAP