Russian President Vladimir Putin on Monday called any possible foreign military intervention against Syria a form of "aggression" that would rattle the entire region and contravene international law.

Putin told a summit of an ex-Soviet security group that he was grateful for its decision to support Moscow's refusal to sanction strikes against President Bashar al-Assad's regime for its alleged use of chemical weapons.

"The members of the Collective Security Treaty Organisation (CSTO) are united in their view that the situation around Syria can only be resolved through political means," ITAR-TASS quoted Putin as saying at a meeting in the southern Russian port city of Sochi.

"Any outside use of force would be a grave violation of international law, which in the language of the UN Charter is referred to as 'aggression'," Putin said.

The Moscow-led bloc also includes Armenia, Belarus, Kazakhstan, Kyrgyzstan and Tajikistan.