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Cameron and Obama warn of 'serious response' to Syria attack

The UK and US have threatened a "serious response" if it emerges Syria used chemical weapons on Wednesday.

Prime Minister David Cameron and President Barack Obama were both "gravely concerned" by "increasing signs that this was a significant chemical weapons attack carried out by the Syrian regime", Downing Street said.

On Saturday, the medical charity Medecins Sans Frontieres (MSF) said hospitals it supports in Syria treated about 3,600 patients with "neurotoxic symptoms", of whom 355 died.

Catherina Moh reports.

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