Armed attackers on Friday killed at least 235 worshippers in a bomb and gun assault on a packed mosque in Egypt's restive North Sinai province, state media reported, the country's deadliest attack in recent memory.

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 and 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 Islamist extremist 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.

UK Foreign Minister Boris Johnson condemned the “barbaric attack” in a post on Twitter, while his French counterpart Jean-Yves Le Drian expressed his condolences to the families of victims of the “despicable attack”.

Ahmed Abul Gheit, head of the Arab League, which is based in Cairo, condemned the “terrifying crime which again shows that Islam is innocent of those who follow extremist terrorist ideology,” his spokesman said in a statement.

There was no immediate claim of responsibility for the attack.

IS targeting Sufis

The militant 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.

IS militants had previously kidnapped and beheaded an elderly Sufi leader, accusing him of practising magic, which Islam forbids, and abducted Sufi practitioners who were 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 also killed more than 100 Christians in church bombings and shootings in Sinai and other parts of Egypt, forcing many to flee the peninsula.

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.