The attack was the largest single targeting of Egyptian civilians and the first on a large mosque congregation since the IS affiliate began its campaign of violence against the state following the military's 2013 overthrow of an elected but divisive Islamist president.
Eyewitnesses reported ambulances ferrying casualties from the scene to nearby hospitals after the Al Rawdah mosque in Bir al-Abed, west of Arish city, was targeted. After at least two explosions, the attackers waited outside the mosque and gunned down worshipers as they tried to flee to safety.
Resident Ashraf el-Hefny said numerous victims were workers at a nearby salt factory who had come for Friday services at the mosque. "The world can not tolerate terrorism, we must defeat them militarily and discredit the extremist ideology that forms the basis of their existence!" the POTUS tweeted.
Hundreds of soldiers and militants have been killed in the conflict, although exact numbers are unclear as journalists and independent investigators are banned from the area. State television put the death toll at 200, with at least 125 others wounded.
The attack is considered to be the deadliest in Egypt's modern history.
As of Friday afternoon, no terror group had claimed responsibility for the attack.
The President, who is celebrating the Thanksgiving holiday with his family at his Mar-a-Lago estate in Florida, said earlier Friday that he would be speaking by phone with Turkish President Recep Tayyip Erdogan about "bringing peace to the mess that I inherited in the Middle East", Efe news agency reported.
Egyptian security forces face nearly daily attacks from ISIS-aligned militants, whom they have been battling in northern Sinai for years.
Britain Secretary of State for Foreign Affairs, Boris Johnson: "Deeply saddened by the abhorrent attack on a mosque in North Sinai, Egypt".
Leaders around the world condemned the mosque attack.
Will be calling the President of Egypt in a short while to discuss the tragic terrorist attack, with so much loss of life.
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