The U.S. ambassador to the United Nations, John Bolton, today demanded immediate cooperation from Syria with a UN probe into the killing.
His comments were echoed by French Foreign Minister Philippe Douste-Blazy. But he said Paris won't consider sanctions on Syria until the inquiry is completed in December.
British Prime Minister Tony Blair also called for a "very serious response" to the report, issued last week.
Meanwhile, thousands of Syrians today took part in state-organized rallies in support of the regime, which denies involvement in the February assassination.