EL-ARISH, Egypt -- Militants bombed a Sufi mosque and fired on worshippers in the volatile Sinai Peninsula during Friday prayers, killing at least 184 people in what appeared to be the latest attack by the area's ISIS affiliate, Egyptian state news agency MENA reports.
The extremists attacked the al-Rawdah mosque in the town of Bir al-Abd, 25 miles from the North Sinai provincial capital of el-Arish, opening fire from four off-road vehicles on worshippers inside during the sermon, three police officers said.
Victims were being transferred to local hospitals, they added, speaking on condition of anonymity because they weren't authorized to brief reporters. They said the ISIS militants had blocked escape routes from the area by blowing up cars and leaving the burning wrecks blocking the roads.
Egypt's state news agency reported the casualty toll, citing "official sources," revising it upward several times following the officials' initial reports. MENA said 125 people were also wounded in the attack.
The attack was the largest single targeting of Egyptian civilians and the first on a large mosque congregation since the ISIS affiliate began its campaign of violence against the state following the military's 2013 overthrow of an elected but divisive Islamist president.
MENA reported that Egypt's presidency declared a three-day mourning period for the attack, as President Abdel-Fattah el-Sissi convened a high-level meeting of security officials.
Cairo's international airport boosted security following the attack, with more troopers and forces seen patrolling passenger halls, conducting searches and manning checkpoints at airport approaches.
Security forces have been battling militants in northern Sinai for years, but attacks to date have focused on military and police assets, although assassinations of individuals ISIS considers government spies or religious heretics are not uncommon.
In September, ISIS militants ambushed a police convoy in Sinai, killing 18 police and wounding seven others in one of the deadliest attacks this year in the restive region bordering Israel and the Gaza Strip.
The ongoing violence in Sinai shows the resilience of the militants there in the face of a years-long campaign to eradicate them by the military and police, which between them command far superior firepower, air support, heavy armor and larger numbers.
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.
Egypt is also facing a growing number of attacks by militants in its Western Desert, including an attack last month that killed 16 police, according to an official tally issued by the Interior Ministry. Security officials have told journalists that dozens more, including high-ranking counterterrorism officers, perished in the Oct. 20 attack some 84 miles southwest of the capital, Cairo.