At least 235 worshipers were killed and 109 others injured when heavily-armed militants bombed a mosque and opened fire on people attending Friday prayers in Egypt's restive North Sinai region, in the deadliest terror attack in the country.
Witnesses said the assailants had surrounded the mosque with all-terrain vehicles then planted a bomb outside.
The gunmen then mowed down the panicked worshippers as they attempted to flee and used the congregants' vehicles they had set alight to block routes to the mosque.
State television reported at least 235 people were killed and 109 wounded in the attack, the scale of which is unprecedented in a four-year insurgency by terrorist groups.
Egypt's presidency declared three days of mourning, state television reported, as President Abdel Fattah al-Sisi met his security ministers to follow developments.
Pictures from the scene show rows of bloodied victims inside the mosque. The blasts from improvised explosive devices caused considerable damage to the mosque.
Speaking to state-run Masriya TV station, Egyptian health ministry spokesman Khalid Mujahid described the incident as a "terrorist attack."
One report said the target appeared to be supporters of the security forces who were praying at the mosque.
No one has yet claimed responsibility for the attack and there is no word yet on what happened to the militants involved. However, it bears the hallmarks of an attack by ISIS, reports said.
There have been regular attacks blamed on militants on the Sinai peninsula since the January 2011 revolution that toppled former president Hosni Mubarak, but this is the deadliest assault of its kind.
The attacks targeting police and military increased after the ouster of Islamist ex-president Mohamed Morsi in 2013 by military following massive protests against his rule.
Over 700 security personnel have been reported killed since then.
The military has launched security campaigns in the area, arrested suspects and demolished houses that belonged to terrorists, including those facilitating tunnels leading to the Gaza Strip.
The Egypt government has announced three days of mourning, even as President Abdel Fattah el-Sisi chaired an emergency meeting with officials to review security situation after the deadly attack.
Egypt has witnessed a series of terror attacks this year claiming scores of lives.
On May 26, gunmen attacked a bus carrying Coptic Christians in central Egypt, killing at least 28 people and wounding 25 others.
On April 9, two suicide bombings at Palm Sunday services at churches in the northern cities of Alexandria and Tanta left 46 people dead.