Worshippers at one of Britain’s biggest mosques reacted to the Fort Hood shooting yesterday by saying Muslims who serve in the Armed Forces are complicit in killing their “brothers and sisters” in Afghanistan.

However, a Muslim ex-soldier who twice served in Afghanistan said that the shooting could not be justified by any mainstream interpretation of Islam. Speaking to The Times after Friday prayers at East London mosque, young Muslim men said the lives of those who follow Islam were of more value than those of non-believers. They gave only their first names, claiming that the authorities might place them under investigation.

Mustapha, 26, from South London, said that the wars in Afghanistan and Iraq were wars against Muslims and he would not consider joining the Army nor encourage fellow Muslims to. “I would not fight against my friends and brothers,” the house-builder said. “The Koran says even if you make allies with non-Muslims and join them to kill Muslims, then you die as a non-believer.”

Asked his views on the killings at Fort Hood, he said: “Killing military members is all right. If you are killing people who are fighting against Muslims then that’s okay.”

Abdul-Hakim, 17, who was born in Britain but spent his formative years in Tanzania, said it was a bigger crime to kill Muslims than non-Muslims such as the soldiers at Fort Hood: “For you to go and kill your own brother, that’s more of a crime than killing them.” Ashraf, a Somali-born A-level student, said that only God could judge the murders committed by Major Hasan. “I’m not saying I justify it,” said the 17-year-old. “But maybe if he was alive he could justify what he done.”

But their views contrasted with those of other Muslims. Zeeshan Hashmi, 30, who was born in Pakistan and served as a British soldier from 2000 to 2005, did two tours in Afghanistan. “People would ask what I would do if I was asked to fight fellow Muslims, but for me it was all about going there to help create a better understanding between peoples,” he told The Times.

In 2006 Mr Hashmi’s brother, Lance Corporal Jabron Hashmi, became the first British Muslim soldier to be killed fighting the Taleban.

“Jabron and I never had any difficulties squaring our identities as both British soldiers and Muslims,” he said.

Mr Hashmi, in his final year as a Cambridge undergraduate, said Major Hasan’s killings would be celebrated by some jihadist extremists but could not be justified by any mainstream interpretation of Islam.“If an individual walks into a facility where people are unarmed and opens fire indiscriminately, that’s an act of terrorism.”

Mr Hashmi said most Muslims would react to the atrocity with horror, but also with concern that it would be used to sow division. “People will feel they’ve got to justify their existence all over again and that’s not fair. Remember Columbine? That was terrible too, but it didn’t make us distrust all schoolchildren, did it?”

Imam Asim Hafiz, a British army chaplain, said that he knew of no Muslims in the Forces who had objected to service in Afghanistan or Iraq. “What we do in Afghanistan is of concern not just to the Muslim community but for British society in general,” he said.

Muslims comprise 0.3 per cent of the forces — about 500 are in uniform — but 2.3 per cent of the population.

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