Russia has warned Western powers against acting unilaterally on Syria amid growing fears over Syria's weapons capability.

The comments, by Russian Foreign Minister Sergei Lavrov, follow remarks by US President Barack Obama in which he indicated that the US would not hold back from responding if Syria used chemical weapons against rebel forces.

Mr Lavrov, speaking during a meeting with a Chinese envoy, said that diplomatic co - operation should be based on "the need strictly to adhere to the norms of international law and the principles contained in the UN Charter".

He said it would be wrong to "allow their violation" and for the US or other Western governments to act unilaterally against Syrian leader Bashar al-Assad.

In the 18 months since the uprising in Syria began, Russia and China have consistently blocked UN action, including vetoing a series of resolution calling on Assad to end the bloodshed.

Concerns have been raised in Israel and the US over the potential for Assad to used chemical weapons on his people, and the possibility that such technology could fall into the hands of the Hizbollah terrorist group.

President Obama said earlier this week: "We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilised.

"We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people."