Prime Minister David Cameron has welcomed President Barack Obama's decision to authorise air strikes on Islamic militants Islamic State (IS) in Iraq, but has ruled out a British military response.

He said in a statement today that he was particularly concerned about the minority Yazidi community trapped on Mount Sinjar, adding that the world had a responsibility to help them "in their hour of desperate need".

"I fully agree with the President that we should stand up for the values we believe in – the right to freedom and dignity, whatever your religious beliefs," he said.

Cameron has asked officials to investigate options for sending relief – especially to the 40,000 people trapped on Mount Sinjar, who are at risk of dying of thirst. However a spokesman ruled out any possibility of the UK joining the US in air strikes.

The UK chaired a meeting of the United Nations Security Council last night, planning possible international measures to help those suffering under IS.

President Obama's decision came after UN Secretary General Ban Ki-Moon called for an international response to the crisis.

Obama said strikes would be used "if necessary" in order to "prevent a potential act of genocide" against the Yazidi community.