Dubai: Russia warned the West on Tuesday against unilateral action on Syria, while Damascus said military intervention was “impossible” a day after US President Barack Obama threatened “enormous consequences” if the regime used chemical or biological arms or even moved them in a menacing way.

Russian Foreign Minister Sergei Lavrov said Moscow and Beijing were committed to “the need to strictly adhere to the norms of international law...and not to allow their violation”.

Syrian Deputy Prime Minister Qadri Jameel dismissed Obama’s threat as media fodder. “Direct military intervention in Syria is impossible because whoever thinks about it ... is heading towards a confrontation wider than Syria’s borders,” he told a news conference in Moscow.

Jameel said the West was seeking an excuse to intervene, likening the focus on Syria’s chemical weapons with the run-up to the 2003 invasion of Iraq by US-led forces on what proved to be groundless suspicions that Saddam Hussain was concealing weapons of mass destruction.

In Syria, heavy shelling and fighting erupted across swathes of the second city of Aleppo and some areas of the capital,

In one of the latest battle zones, Syrian troops and tanks overran the Damascus suburbs of Muadamiya on Tuesday, killing at least 20 young men and burning shops and houses before pulling back, residents and opposition activists said.

Meanwhile, at least three people were killed and scores injured in Syria-linked Lebanon clashes.

In Paris, officials said the conflict has turned Syria into one of the world’s worst humanitarian crises, exacerbated by attacks on aid workers.

“There are 2.5 million people in need of aid now inside Syria, and 1.2 million have been displaced from their homes, so on that scale it’s right up there with the worst crises in the world today,” said David Robinson, a top official at the State Department’s Bureau of Population, Refugees and Migration.