"More than 100 cruise missiles and air-to-land missiles were fired by the US, Britain and France from the sea and air at Syrian military and civilian targets," the ministry said in a statement quoted by RIA Novosti news agency, adding that "a significant number" were shot down by Syrian air defences.

It said that 12 cruise missiles were fired at an airfield close to Damascus and all were intercepted by Syria's air defences.

"Russian air defence systems located on Syrian territory have not been used to counter the missile strikes", it said.

It said earlier that none of the Western strikes in Syria had hit areas covered by Russia's air defences around its Hmeimim air base and naval facility in Tartus.

The Russian military said the missiles were fired from US ships in the Red Sea as well as from tactical aircraft over the Mediterranean and by US strategic bombers from the Al-Tanf base in southeastern Syria.

The US, France, and Britain announced a joint operation against Syria's government, a week after an alleged chemical attack outside the capital Damascus that was said to have left more than 40 people dead.