Kerry discussed attack with Syrian FM: US official

WASHINGTON, District of Columbia - US Secretary of State John Kerry spoke Thursday with Syria's foreign minister about an alleged chemical weapons attack a day earlier that reportedly killed hundreds of civilians, an American official said.

Kerry discussed the attack on rebel-held areas near Damascus with Walid al-Muallem "to make clear that if, as they claimed, the Syrian regime has nothing to hide, it should have allowed immediate and unimpeded access to the site rather than continuing to attack the affected area to block access and destroy evidence," the official said.

The top US diplomat also made a series of calls about evidence relating to the attack, speaking Saturday to the foreign ministers of Jordan, Turkey and Saudi Arabia, as well as the secretary-general of the Arab League.

"In all these calls, the Secretary emphasised the importance of quickly determining the facts and underscored the seriousness and gravity of any chemical weapons use," said the US official, who spoke on condition of anonymity.

US President Barack Obama is under mounting pressure to act following reports of the alleged chemical weapons attack, which Doctors Without Borders said had killed 355 people due to "neurotoxic" symptoms.

Opposition groups say the reported attack was carried out by Syrian President Bashar al-Assad's forces and that it killed more than 1,000 people.