Armed assailants killed at least 85 people in an attack on a mosque in Egypt's volatile northern Sinai Peninsula during Friday prayers, MENA state news agency said, citing an official source. At least 80 more people were wounded in the attack that targeted worshipers near the Sinai capital of el-Arish, the report said.

According to the Egyptian health ministry, there was a high death toll because the militants targeted the ambulances transporting the victims of the attack on al-Rawdah mosque in the town of Bir al-Abd, 40 km from el-Arish.

Earlier, officials said militants in four off-road vehicles bombed the mosque and fired on worshipers during the sermon segment of the prayers. 

ISIS' Egypt branch has killed hundreds of policemen and soldiers, and also civilians accused of working with the authorities, in attacks in the north of the Sinai peninsula. The victims of Friday's attack included civilians and conscripts praying at the mosque. Egypt's government declared three days of mourning after the attack.

Egypt announced a three-day mourning period for the victims of the terrorist attack that took place on Friday in the vicinity of Al-Rawdah mosque, West Arish city, killing at least 54. A number of militants stormed Al-Rawdah mosque in west Arish City during Friday prayers, and detonated an explosive device. 

The Ministry of Health earlier confirmed that 75 were injured in the attack, adding that many were transported to Bir al-Abed hospital in North Sinai. The mosque was also damaged as a result of the bomb. Eyewitnesses said that the militants set fire to cars belonging to local residents and blocked a road in Al-Rawdah Village. 

Security and medical sources in the area reported that the police halted traffic on Arish-Qantara Road, and deployed ambulance vehicles to transport the injured to the hospital. A state of emergency has been ongoing in Egypt since the Palm Sunday twin church attack last April, which killed 45 Copts including children.

President Abdel Fatah al-Sisi said justice will be served and will reach the perpetrators, accomplices, inciters and funders of the attack on the Friday Rawda Mosque in Arish. The Egyptian president said in a statement the attack will be followed with a "deterring and firm punishment," adding that the "pain felt by the Egyptian people will not be in vain."  He also emphasized that Egypt will win in its war against terror "honorably and forcefully."

On his hand, Grand Imam of Al-Azhar and Chairman of the Muslim Council of Elders Ahmad el-Tayyeb has strongly condemned the Arish mosque militant attack. Informed sources told Egypt Today that 54 were killed and 75 were injured in a militant attack at a mosque in Arish City, North Sinai in Friday.