Richard Dawkins has said the Peshawar massacre by the Taliban is evidence of how religion leads to evil.
More than 130 children and nine members of staff were killed during the massacre by the seven members of Tehrik-e-Taliban (Pakistan arm of the Taliban).
The Taliban said they targeted the area in response to the Pakistan army killing innocent children and families of their fighters.
Dawkins, an outspoken atheist, has compared how some people use faith to justify their actions to Nazism.
Via Twitter he said: "Very few faith-heads are as evil as Taliban or IS [Islamic State]. Yet what else but faith is capable of making people do such evil? Mental illness can drive a lone nutter to it. But an organised group needs an extreme motivation – faith, in something like a god or Nazism."
The evolutionary biologist has previously described Islam as "one of the great evils in the world" and said faith is "lethally dangerous nonsense".
In the wake of the 9/11 terror attacks in New York, he told the Guardian: "Dangerous because it gives people unshakeable confidence in their own righteousness. Dangerous because it gives them false courage to kill themselves, which automatically removes normal barriers to killing others.
"Dangerous because it teaches enmity to others labelled only by a difference of inherited tradition. And dangerous because we have all bought into a weird respect, which uniquely protects religion from normal criticism."