BRUSSELS, Aug 21 (Reuters) - The European Union called for a "thorough and immediate" investigation of an alleged chemical attack in Syria after Syrian rebels said hundreds of people were killed on Wednesday in a gas attack and shelling by President Bashar al-Assad's forces.
"We have seen with grave concern the reports of the possible use of chemical weapons by the Syrian regime. Such accusations should be immediately and thoroughly investigated," a spokesman for EU foreign policy chief Catherine Ashton said.
"The EU reiterates that any use of chemical weapons, by any side in Syria, would be totally unacceptable."
(Reporting by Justyna Pawlak; Editing by John O'donnell)