A bomb explosion ripped through the Rawda mosque frequented by Sufis roughly 40 kilometres west of the North Sinai capital of El-Arish before gunmen opened fire on those gathered for weekly Friday prayers, officials said.
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.
Egyptian air force jets later destroyed vehicles used in the attack and "terrorist" locations where weapons and ammunition were stocked, an army spokesman said on Friday.
The planes "destroyed several vehicles used in the attack," Tamer el-Refai said.
The state prosecutor's office said in a statement that 235 people were killed and 109 wounded in the attack, the scale of which is unprecedented in a four-year insurgency by Islamist extremist groups.
Between ten and 20 armed attackers "entered the mosque, killing more people than they injured," Magdy Rizk, who was wounded in the attack, told AFP.
Source: AFP, Getty
"They were wearing masks and military uniforms," he said, adding that the area was predominantly Sufi and that locals have received threats from extremist groups.
US President Donald Trump condemened on Twitter the "horrible and cowardly terrorist attack on innocent and defenseless worshippers."
A furious Egyptian President Abdel Fattah al-Sisi declared three days of mourning and pledged to "respond with brutal force" to the attack.
"The army and police will avenge our martyrs and return security and stability with force in the coming short period," he added in a televised speech.
Russian President Vladimir Putin sent condolences to Sisi, calling the attack "striking for its cruelty and cynicism", while condemnations poured in from Israel, Iran, Saudi Arabia and other countries.
UK foreign minister Boris Johnson decried the "barbaric attack", while his French counterpart Jean-Yves Le Drian labelled it "despicable".
Pope Francis and Egypt's highest Muslim religious authority joined in the condemnation.
"His Holiness joins all people of good will in imploring that hearts hardened by hatred will learn to renounce the way of violence," the pope's office said.
The grand imam of Cairo's Al-Azhar, Sheikh Ahmed el-Tayeb, condemned "in the strongest terms this barbaric terrorist attack".
Hundreds have died after militants assaulted a crowded mosque in Egypt. Source: AAP
'No Australians known to be affected'
Prime Minister Malcolm Turnbull has condemned the "appalling and barbaric" terrorist attack.
The Australian Embassy in Cairo has been advised by Egyptian authorities that no Australians are known to have been affected by the attack.
"We send our condolences to the families of the victims and wish a speedy recovery for the injured," Mr Turnbull wrote on Twitter on Saturday.
"We are resolute in our determination to defeat Islamist terrorism & keep Australians safe."
Opposition Leader Bill Shorten and Labor's foreign affairs spokeswoman Penny Wong also condemned the attack, the latest in a series of assaults on places of worship - namely against Christian Copts in churches in Cairo, Alexandria and Tanta.
"Labor stands once more with all people of goodwill, of all faiths who utterly reject those who would seek to divide us through terror and violence," they said in a joint statement.
"An attack on any place of religion is an attack on freedom of religion everywhere and Labor expresses our support and deepest sympathy for the victims, their families, and the Egyptian people."
A damaged car at the site of the Egypt Sinai mosque bombing in Al-Arish, Egypt on November 24, 2017. Source: Getty
'Gaza Strip to remain closed after attack'
The Gaza Strip's border crossing with Egypt that was due to reopen Saturday will remain closed until further notice following the bloody attack in neighbouring Sinai, an official told AFP.
Gaza's Rafah border crossing with Egypt had been due to reopen on Saturday for three days.
But the official in Gaza, speaking on condition of anonymity, said it will remain closed.
"The Egyptian side informed us that Rafah will not reopen on Saturday because of the tragic events in Northern Sinai," the official added.
The border reopened last Saturday for three days for the first time since the transfer of control of Gaza crossing points from the Islamist Hamas movement to the Palestinian Authority on November 1.
It had been closed since August, and the reopening allowed patients, students and stranded people to leave the Palestinian enclave.
Gaza has been subject to Israeli blockade for a decade, and for years to the almost permanent closure of its border with Egypt.
Hamas took power by force in June 2007 after a week of bloody clashes with Palestinian president Mahmud Abbas's Fatah.
The transfer of control of border crossings is a major test for a reconciliation deal reached in Cairo on October 12, after multiple previous attempts at Hamas-Fatah reconciliation over the past decade failed.
Malcolm Turnbull and Bill Shorten have condemned a "horrific" terror attack on a mosque in Egypt. (AAP) Source: AAP
'No claim of responsibility'
There was no immediate claim of responsibility for the bloodshed.
The Islamic State group's 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.
They have also targeted followers of the mystical Sufi branch of Sunni Islam as well as Christians.
The victims of Friday's attack included civilians and conscripts praying at the mosque.
A tribal leader and head of a Bedouin militia that fights IS told AFP that the mosque is known as a place of gathering for Sufis.
The Islamic State group shares the puritan Salafi view that Sufis are heretics for seeking the intercession of saints.
The jihadists had previously kidnapped and beheaded an elderly Sufi leader, accusing him of practising magic which Islam forbids, and abducted Sufi practitioners later released after "repenting."
An IS propaganda outlet had published an interview earlier with the commander of its "morality police" in Sinai who said their "first priority was to combat the manifestations of polytheism including Sufism."
The group has 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 jihadists who pledged allegiance to IS in November 2014.
IS regularly conducts attacks against soldiers and policemen in the peninsula bordering Israel and the Palestinian Gaza Strip, although the frequency and scale of such attacks has diminished over the past year.
The jihadists have since increasingly turned to civilian targets, attacking not only Christians and Sufis but also Bedouin Sinai inhabitants accused of working with the army.
Aside from IS, Egypt also faces a threat from Al-Qaeda-aligned jihadists who operate out of neighbouring Libya.
A group calling itself Ansar al-Islam -- Supporters of Islam in Arabic -- claimed an October ambush in Egypt's Western Desert that killed at least 16 policemen.
Many of those killed belonged to the interior ministry's secretive National Security Service.
The military later conducted air strikes on the attackers, killing their leader Emad al-Din Abdel Hamid, a most wanted jihadist who was a military officer before joining an Al-Qaeda-affiliated group in Libya's militant stronghold of Derna.
