Bells rang out in Coptic Orthodox churches across Egypt today at 12 noon local time in solidarity with the victims of the terrorist attack on the Sinai mosque yesterday.

Up to 300 people were killed when militants targeted worshippers in a coordinated gun and bomb attack on al-Rawdah mosque in Bir al-Abed, west of Arish city in the Sinai region.

A bomb exploded and sent worshippers fleeing for safety, only to be fired on by the terrorists as they ran. Ambulances heading to the mosque to treat the wounded were also fired on.

The attack on the Sufi congregation – regarded as heretical by hard-line Sunnis – echoed attacks on Christian churches that have left many dead and others fearing for their lives. Announcing the ringing of bells, the head of the Coptic Orthodox Church in Britain, Bishop Angaelos, tweeted that the mosque attack represented 'Different individuals, different communities, different faith...same senseless destruction and pain.'

Egypt's military said today it had carried out air strikes and raids overnight against militants held responsible.

'The air force has over the past few hours eliminated a number of outposts used by terrorist elements,' the army said.

Egypt's President Sisi, a former armed forces commander who supporters see as a bulwark against Islamist militants, promised the 'utmost force' against those responsible for Friday's attack. Security has been a key reason for his supporters to back him, and he is expected to run for re-election next year.

Among those condemning the outrage was the general secretary of the World Council of Churches, Rev Dr Olav Fykse Tveit, who wrote to the Grand Imam of Al-Azhar University in Cairo, Dr Ahmad al-Tayyeb, saying: 'We must condemn this attack on our Muslim brothers and sisters as a devastating disregard for human life, and so painful to confront when people who are worshipping are targeted. We stand beside you, we walk with you and we will not allow this heinous act to divide us.'

He said: 'We condemn strongly this tragic attack against our Muslim brothers during prayer time, in a place of worship dedicated to peace and devotion.'