Foreign Secretary Boris Johnson has called for International Criminal Court (ICC) procedures against any war crimes - such as airstrikes against hospitals and aid workers - in Syria.
Mr Johnson told MPs that "there could be advantage in ICC procedures".
In a warning to those responsible, he said: "I would remind this House that in recent history war criminals have been successfully prosecuted decades after their offences.
"Those who are conducting this bombing and in my view culpable of these crimes should realise that the mills of justice grind slowly but they grind small."
"The only realistic solution" to the Syrian conflict is a ceasefire followed by a political solution, Mr Johnson added.
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