Dr Rowan Williams, the Archbishop of Canterbury, defended Pope Benedict XVI, saying: "There are elements in Islam that can be used to justify violence, just as there are in Christianity and Judaism." He added: "The Pope has issued an apology, and I think his views on this need to be judged against his entire record, where he has spoken very positively about dialogue." The Pope, who has apologised for the offence caused to Muslims, is expected to elaborate further tomorrow. Cardinal Tarcisio Bertone, his Secretary of State, said that papal nuncios (ambassadors) in Muslim countries had been instructed to explain personally to political and religious leaders that the remarks had been misunderstood and taken out of context. Security around St Peter's Square remained tight as al-Qaeda militants in Iraq vowed to "conquer Rome". The Mujahidin Shura Council, an umbrella group for Sunni Islamists, said in a statement: "We tell the worshipper of the Cross (the Pope) that you and the West will be defeated . . . May God enable us to slit their throats, and make their money and descendants the bounty of the mujahidin." Another militant group in Iraq, Ansar al-Sunnah, added: "The day is coming when the armies of Islam will destroy the ramparts of Rome." Effigies of the Pope were burnt from Basra in Iraq to Muzaffarabad in Kashmir. The president of the Islamic Association of China said that the Pope had insulted both Islam and the Prophet Muhammad. In the Vatican, dismay over the crisis was mingled with grim irony that a quotation accusing Islam of using violence had been greeted with violence. Cardinal George Pell, the Archbishop of Sydney, said: "The violent reactions in many parts of the Islamic world justified one of Pope Benedict's main fears . . . They show the link for many Islamists between religion and violence, their refusal to respond to criticism with rational arguments, but only with demonstrations, threats and actual violence." In London yesterday Anjem Choudary, a militant Muslim lawyer, said during a protest outside Westminster Cathedral that those who insulted Islam should be killed. Cardinal Keith O'Brien, Archbishop of St Andrews and Edinburgh, said: "We pray that calm will return and our two religions can carry on working together." The Pope had referred to remarks by the 14th-century Byzantine Emperor Manuel II Paleologus, who said that everything the Prophet Muhammad brought was evil, "such as his command to spread by the sword the faith he preached". The Pope said that the quotation did not represent his personal views.