Islamist militants claiming loyalty to ISIS have released a video appearing to show the beheading of 21 Coptic Christians who were taken hostage in Libya several weeks ago. The video shows men apparently being beheaded after being forced to kneel next to the Mediterranean Sea. A militant says they are sending a message "from the south of Rome". At the end of the footage the same English-speaking fighter raises his knife to the water and says ISIS would "conquer Rome". This morning Egypt and the Libyan government said they had launched air strikes in retaliation against Islamic State targets. Egypt said the strikes were intended "to avenge the bloodshed and to seek retribution from the killers", adding: "Let those far and near know that Egyptians have a shield that protects them." Most of the victims are believed to be Egyptian. Bishop Angaelos, leader of the Coptic Orthodox church in Britain, said the massacre showed "not only a disregard for life but a gross misunderstanding of its sanctity and equal value in every person". He said his prayers were with the victims' families and also with the militants who carried out the atrocity. "We pray for an end to the dehumanisation of captives who become mere commodities to be bartered, traded and negotiated with," the bishop said. In the video released by the militants, an Islamist says in English: "All crusaders: safety for you will be only wishes, especially if you are fighting us all together. Therefore we will fight you all together... The sea you have hidden Sheikh Usama Bin Laden's body in, we swear to Allah we will mix it with your blood."