0742 GMT January 25, 2020
The state prosecution said up to 30 terrorists in camouflage flying Daesh’s black banner had surrounded the mosque in North Sinai and proceeded to massacre the worshippers during weekly Friday prayers, AFP reported.
Twenty-seven children were among the dead, it said.
Daesh, which is conducting a deadly insurgency in the Sinai, has not claimed responsibility for the attack, but it is the main suspect as the mosque is associated with followers of the mystical Sufi branch of Sunni Islam.
Funerals for the victims were held overnight and many were buried unwashed in their bloodied clothes, according to the Islamic burial practices for martyrs, security and medical officials said.
President Abdel Fattah al-Sisi declared three days of mourning and vowed to "respond with brutal force" to the attack, among the deadliest in the world in two decades.
"The army and police will avenge our martyrs and return security and stability with force in the coming short period," he said in a televised speech.
Hours later Egyptian air force jets pursued the "terrorists and discovered several vehicles used in the terrorist attack, killing those inside near the vicinity of the attack," an army spokesman said in a statement.
The state prosecutor's office said in a statement that 305 people were killed and 128 wounded in the assault on the mosque roughly 40 kilometers (25 miles) west of the North Sinai capital of Al-Arish.
It said the attackers, with long beards and hair often seen on terrorists, had arrived in five all-terrain vehicles to surround the mosque.
Witnesses said they heard gun shots and explosions before the assailants entered the mosque, according to the prosecution.
One of the wounded, Magdy Rizk, said assailants wore masks and military uniforms, and that extremists had previously threatened people in the area.
Relatives visited victims in hospital in the city of Ismailia near the Suez Canal where the wounded were taken for treatment.
Sheikh Ahmed el-Tayeb, the grand imam of Cairo's Al-Azhar, Egypt's highest institution of Sunni Islam, condemned "in the strongest terms this barbaric terrorist attack".
The Egypt branch of Daesh 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.
They have also targeted Sufis as well as Christians.
A tribal leader and head of a Bedouin militia that fights Daesh said that the mosque is known as a place where Sufis gather.
The group has also killed more than 100 Christians in church bombings and shootings in Sinai and other parts of Egypt, forcing many to flee the peninsula.
The military has struggled to quell the terrorists who pledged allegiance to Daesh in November 2014.
The terrorists have since increasingly turned to civilian targets, attacking not only Christians and Sufis but also Bedouin Sinai inhabitants accused of working with the army.
The group also claimed the bombing of a Russian plane that killed all 224 people on board after takeoff from the Egyptian Red Sea resort of Sharm Al-Sheikh on October 31, 2015.