A relative of one of the victims reacts after a church explosion killed at least 21 in Tanta, Egypt, April 9, 2017. (Xinhua/Reuters Photo)

CAIRO, April 9 (Xinhua) -- At least 21 people were killed and 59 injured in an explosion inside a church in the Egyptian Nile delta city of Tanta on Sunday, the Egyptian health ministry said.

An explosive device was planted in the front seat of the church, State-run TV quoted a security sources as saying.

Eyewitnesses said the explosion struck the crowd and caused destruction of a wall.

The bombing came while the Copt marks the Palm Sunday. The death toll may increase because wounded people are in critical conditions.

There was no immediate claim of responsibility.

President Abdel Fattah Al-Sisi ordered all the military hospitals to receive the wounded of the blast.

Some 26 ambulances have been deployed at the Mar Girgis Coptic Church, about 120 kilometres north of Cairo, Magdy Awad, head of the Ambulance Authority told Xinhua.

The security forces intensified its presence around other churches, the Egyptian interior ministry said in a statement.

The prosecutor general ordered a team to move to the scene of the attack and to open investigation swiftly, while the prime minister and the interior minister have also travelled to Tanta.

Coptic Christians make up about 10 percent of Egypt's population. They have largely coexisted peacefully with the majority-Muslim public for centuries.

At the end of 2016, at least 29 people were killed and 31 wounded in an explosion that targeted the Cathedral of Saint Mark in the Abbasia district in Cairo.