The death toll from an attack on a mosque in Egypt's Sinai rose to 305 including 27 children, the state prosecution said on Saturday (November 25^th) in a statement detailing the gruesome massacre.

It said there were between 25 and 30 attackers with long hair and beards, dressed in camouflage and flying a black banner with the Muslim profession of faith on it, which could be a description of the Islamic State group's flag.

They surrounded the mosque and opened fire on the worshippers on Friday, it said.

Gunmen attacked the Rawda mosque in the North Sinai, killing more than 300 people. (AFP/STRINGER)

U.S. 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".

"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".

VNF/AFP