The US President Barack Obama says claims of chemical weapons use in Syria will be investigated.

It comes as rebels call on the international community to take action after further intelligence suggests forces loyal to President Bashar al-Assad have used chemical weapons.

Syrian government officials have denied the use of the weapons despite claims of video evidence.

The video was taken in a hospital in Aleppo and shows men and women frothing at the mouth and twitching from the effects of the nerve agent. It was posted online just over a week ago.

Last week, the British Foreign Office says it has "limited but persuasive evidence" the nerve agent sarin has been used. While the US says it believes "with some degree of varying confidence" chemical attacks have taken place.

In Israel last month, Obama repeated his warning that if chemical weapons are used he would take action.

And speaking at a White House Conference a short time ago, US President Barack Obama says if proven - it would be "a game-changer".