Syrian regime troops aided by Russian air strikes have fought their fiercest clashes with rebels in weeks, as US-led coalition forces parachuted ammunition to rebels battling jihadists in the north of the country.

Meanwhile, the UN's peace envoy to Syria said he was heading to Moscow to promote a political end to the conflict, despite Russia intensifying its raids.

Key points: Syrian troops make gains in Hama province

Syrian troops make gains in Hama province US drops 50 tonnes of ammunition to rebels

US drops 50 tonnes of ammunition to rebels UN envoy pushes plans for political settlement

In a complex conflict involving several foreign players, Moscow has sided militarily with president Bashar al-Assad against his armed foes, branding them "terrorists".

Washington and European states have called for him to be ousted and expressed their support for what they term "moderate" rebel groups while seeking to eliminate the Islamic State (IS) jihadist group.

On Monday, the US said coalition aircraft had dropped ammunition to Syrian Arab groups fighting IS in the north of the country.

"Coalition forces conducted an airdrop Sunday in northern Syria to resupply local counter-ISIL ground forces as they conduct operations against ISIL," US Central Command spokesman Colonel Patrick Ryder said, using an alternative acronym for IS.

Speaking on condition of anonymity, a US official said the drop included 50 tonnes of ammunition.

In the latest fighting, Syrian troops and allied forces gained ground in the central province of Hama, advancing on the strategic Sahl al-Ghab plain backed by Russian air power.

Syria's army command said regime forces had captured Kafr Nabuda village in Hama, extending their advance around the key Damascus-Aleppo highway.

And the Syrian Observatory for Human Rights said the Syrian army had captured Mansoura village in the Sahl al-Ghab plain.

"The clashes are the fiercest since the Russian air campaign began on September 30," the Observatory's Rami Abdel Rahman said, adding that dozens of Russian air strikes hit Sahl al-Ghab on Monday.

On Tuesday, China's top newspaper accused both the United States and Russia of replaying their Cold War rivalry by engaging in military action in Syria, saying they needed to realise that era is over and should instead push for peace talks.

The People's Daily, the official paper of China's ruling Communist Party, said in a commentary that the United States and Russia seemed to be using Syria as a proxy for diplomatic and military competition, as during the Cold War.

"The United States and the Soviet Union used all sorts of diplomatic, economic and military actions on the soil of third countries, playing tit-for-tat games to increase their influence — it's an old scene from the Cold War," the newspaper wrote in a commentary.

"But we're in the 21st century now, and people need to get their heads around this," it added.

Russians hit 53 targets in past day

Sahl al-Ghab lies at the intersection of the provinces of Hama, Latakia and Idlib, and has been a major target for Russian strikes.

Idlib province is controlled by the powerful Army of Conquest rebel alliance which includes Al Qaeda affiliate Al-Nusra Front.

They have sought to advance into Sahl al-Ghab and on towards Latakia province, the coastal stronghold of the regime and the home to Mr Assad's ancestral village.

Syria's army command also reported advances in northern Latakia province and said regime forces had taken control of the "duty free zone" outside Aleppo in the north.

Russia said its air force had hit 53 targets in Syria in the past 24 hours, in Hama, Homs, Latakia and Idlib provinces.

On Monday, UN peace envoy to Syria Staffan de Mistura said he would head to Moscow then to Washington, as he struggles to push his initiative for a political settlement in Syria.

Also on Monday, EU foreign ministers demanded Moscow stop targeting non-jihadist rebels and said lasting peace in Syria was impossible without a transition from Mr Assad's rule.

"The recent Russian military attacks that go beyond Daesh (IS) and other UN-designated terrorist groups, as well as on the moderate opposition, are of deep concern and must cease immediately," the 28 ministers said in a statement.

More than 240,000 people have been killed in the conflict and upwards of 4 million Syrians have become refugees.

AFP