21 people have been killed and more than 50 others were injured during a bomb explosion inside a church in a city north of Cairo Sunday, according to the country's health ministry.

"21 were killed and 59 others injured in the blast," ministry spokesman Khaled Mujahed said in a statement.

The blast took place during a Palm Sunday mass at the Mar Girgis Coptic Church in the city of Tanta about 120 kilometres (75 miles) from Cairo, an interior ministry official said. Palm Sunday is a Christian feast commemorating the entry of Jesus Christ into Jerusalem.

A search for further explosives is underway in the site, the Interior Ministry said.

No group has yet claimed responsibility for the bombing.

The attack in the Nile Delta town of Tanta was the latest in a series of assaults on Egypt's Christian minority, which makes up around 10 percent of the population and has been repeatedly targeted by terrorist groups. It comes just weeks before Pope Francis is due to visit Egypt.