At least 41 people have died in a fire at a church in the Egyptian city of Giza, officials say.

An electrical fire broke out as 5,000 worshippers gathered for mass at the Coptic Abu Sifin church, security sources told Reuters.

The fire blocked an entrance, causing a stampede, the sources said, adding that many of those killed were children. Dozens are thought to be injured.

Fire services say the blaze has been brought under control.

The exact cause of the fire is not clear.

"People were gathering on the third and fourth floor, and we saw smoke coming from the second floor. People rushed to go down the stairs and started falling on top of each other," Yasir Munir, a worshipper at the church, told Reuters.

"Then we heard a bang and sparks and fire coming out of the window," he said, adding that he and his daughter were on the ground floor and able to escape.

Egyptian President Abdel Fattah al-Sisi offered his "sincere condolences to the families of the innocent victims that have passed on to be with their Lord in one of his houses of worship".

The prosecutor's office said it had sent a team to the scene to investigate the cause of the blaze.

Giza lies just across the Nile from Cairo and is part of the Greater Cairo metropolis.

Coptic Christians make up at least 10 million of Egypt's 103 million people.

Copts claims they face discrimination and play a lesser part in Egyptian public life than their numbers justify.