Egyptian president Abdel Fattah El Sisi offered words of assurance to the country's Coptic Orthodox Christians on Saturday as they held Christmas Eve mass at a massive new cathedral after a year of deadly extremist attacks on the community.

Mr El Sisi wished the community a merry Christmas, telling them that the country would prevail over the extremists.

"You are our family, you are from us, we are one and no one will divide us," the president said in short speech before the liturgy led by Pope Tawadros II.

"We, with the grace of God, are offering a message of peace and love from here, not just to Egyptians or to the region, but to the entire world," Mr El Sisi said, drawing ululations and chants from some of the congregation and visitors.

The new cathedral, named Christ's Nativity, is located in Egypt's new Administrative Capital, a 45-billion-dollar, under-construction project some 45 kilometres east of Cairo. The Christmas Eve mass will consecrate the new cathedral and mark the first time in living memory that the liturgy is not held at St Mark's Cathedral, the seat of the orthodox church in central Cairo.

The new cathedral can house up to 9,000 worshippers and is touted as the largest in the Middle East.

Mr El Sisi arrived shortly after nightfall, as silver lights twinkled on the cathedral's dome piercing the surrounding darkness. As a former army chief turned president, he is viewed by most of Egypt's Christians as their protector and ally in the face of extremists.

The cathedral's bells tolled as Pope Tawadros received Mr El Sisi outside the cathedral and they walked inside together. Women ululated in jubilation and many in the congregation waved Egyptian flags or threw white rose buds at the smiling president, who waved back and shook hands with some of them.Police were joined by soldiers as security was tightened around the country's churches ahead of services following a spate of attacks that began in 2016.

More than 100 Christians have been killed in the violence, including a shooting at a church south of Cairo just last week claimed by ISIL.

While the extremists have also taken aim at other civilians, including more than 300 Muslim worshippers massacred at a mosque last November, they have focused on the ancient Coptic community.

In December 2016, an ISIL suicide bomber killed almost 30 worshippers at a church in Cairo located in the Saint Mark's Cathedral complex, the seat of the Coptic papacy.

In the Sinai Peninsula, where the Egptian affiliate of ISIL is based, hundreds of Christians were forced to flee in January and December after a wave of assassinations.

ISIL suicide bombers killed more than 40 people in twin church bombings in April and shot dead almost 30 Christians a month later as they headed to a monastery.

The year ended with an ISIL follower killing nine people in an attack on a church in a south Cairo suburb.

Copts, who make up about 10 per cent of Egypt's 93 million people, have long complained of discrimination and intermittent sectarian attacks.