Syrian forces made advances against rebels in Hama and Latakia provinces Saturday as the US and Russia declared "progress" in talks designed to avoid accidents in war-torn Syria's increasingly crowded air space.

The Pentagon said more talks with Moscow were planned after positive discussions on Saturday aimed at preventing military mistakes, a decision confirmed by the Russian defence ministry, which described negotiations so far as as "professional and constructive".

Western governments claim the vast majority of Russian strikes have targeted rebel groups other than Islamic State (IS) -- the focus of their own air campaign -- in an attempt to defend President Bashar al-Assad's rule.

In Hama, with Russian air support and that of militias on the ground, regime forces captured several areas.

Assad's troops seized Atshun village from opposition fighters, including Al-Qaeda affiliate Al-Nusra Front, state television and the Syrian Observatory for Human Rights said, with heavy fighting reported as they sought to push northwest and take a neighbouring hilltop.

They appeared to be targeting the town of Khan Sheikhun, just across the provincial border in Idlib on a highway connecting Aleppo and Damascus.

The road is cut by rebels in several places north of Khan Sheikhun, and a military source said they had taken the Sukayk hills overlooking the road.

Hama province has been a key target for Russian air strikes that began on September 30, along with parts of the neighbouring provinces of Latakia and Idlib.

- Russia hits 'terrorist' camps -

Russia's strikes appear intended to prevent any advance by the Army of Conquest alliance, which includes Al-Nusra, that holds Idlib and has sought to push into Hama and Latakia.

The Observatory said there was heavy fighting in north and northwestern Latakia, and that government forces were advancing.

In Moscow, Russia's defence ministry said its forces had hit 55 IS targets in the past 24 hours.

The strikes -- in Damascus, Aleppo, Hama, Raqa and Idlib provinces -- destroyed 29 training camps for "terrorists", 23 defensive positions, two command centres and an ammunition depot.

Rebels and their backers say Hama, Idlib and Latakia have little or no IS presence, and accuse Russia of targeting moderate and Islamist opposition fighters more than the jihadist group.

Russian warplanes struck both Latakia and Idlib Friday and Saturday, including a raid in Idlib that destroyed a base belonging to a rebel group that has received US weapons, it said.

The US-led coalition said it carried out five strikes against IS in Syria and another 20 in Iraq, but the Russian air campaign has complicated its efforts.

Washington expressed alarm this week after Moscow failed to quickly answer proposals made during previous talks, even as Russia launched cruise missiles from the Caspian Sea and repeatedly violated Turkish air space.

US officials were furious after Russia only gave them a vague, verbal "heads-up" about an hour before Moscow launched its bombing campaign over Syria.

In the northern province of Aleppo, rebels battled to reverse an advance by the Islamic State group that brought the jihadists to within a few kilometres (miles) of Syria's second city.

Islamist rebels including the powerful Ahrar al-Sham group recaptured one of several villages seized by IS in a Friday advance, the Observatory said.

- Explosives factory blast -

The monitor added that rebels were battling to retake a second village from the jihadist group, which now has forces within 10 kilometres (six miles) of Aleppo city.

The IS offensive has brought the jihadists closer than ever to Aleppo, threatening to further complicate the situation in Syria's one-time commercial capital, long divided between government and rebel control.

At the same time, government forces attacked IS in several villages around the Kweires military airport in a bid to break a months-long siege, the Observatory said.

Elsewhere in the province, the Observatory said a powerful blast ripped through an explosives factory and weapons depot in the IS-held town of Al-Bab.

The cause of the explosion was unclear, although unidentified warplanes were seen overhead at around the time of the blast.

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