BRUSSELS (AFP) - Nato Secretary General Anders Fogh Rasmussen on Friday welcomed a "clear" US statement accusing the Syrian regime of using chemical weapons and said Damascus must let the United Nations (UN) investigate the allegations.

"I welcome clear US statement. Urgent that Syria regime should let UN investigate all reports of chemical weapons use," he said on his official Twitter feed.

He said the international community had made clear that the use of chemical weapons by Syrian President Bashar Al Assad was "completely unacceptable" and a "breach of international law".

"Nato Patriots will ensure effective protection of Turkey against any Syria missile attack, chemical or not," he said, referring to the air defence missiles that Nato has stationed in Turkey.

The Nato chief's comments came the day after President Barack Obama's administration said it had concluded that Syrian regime forces had used banned arms, including the nerve gas sarin, in attacks that killed up to 150 people.

The White House also promised "military support" to Syrian rebel forces.