Western strikes early Saturday hit Syrian military bases and research centres in and around the capital and the country's centre, a monitor said, as the US, France, and Britain announced a joint operation.
"The Western coalition strikes targeted scientific research centres, several military bases, and the bases of the Republican Guard and Fourth Division in the capital Damascus and around it," said the Britain-based Syrian Observatory for Human Rights.
Observatory chief Rami Abdel Rahman later said that a military research centre and depot near the city of Homs in the country's centre were also hit.
He had no immediate details on casualties.
The US, France, and Britain announced a joint operation against Syria's government, a week after a suspected chemical attack outside the capital Damascus left more than 40 people dead.
The world leaders announced that the strikes targeted positions linked to the chemical weapons facilities of the Syrian government.
Moments after the announcement, loud blasts could be heard from the capital and large plumes of smoke emerged from its northern and eastern edges.
Syrian state media reported the joint operation hit a research centre northeast of the capital as well as other military installations around Damascus, but said missiles targeting army depots in Homs had been intercepted.
The US and Europe have both slapped sanctions on the Syrian Scientific Studied and Research Centre for its links to chemical weapons production in Syria.
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