Beirut (AFP) - A commando operation backed by Russian warplanes and helicopters has killed 25 members of the Islamic State jihadist group in central Syria, a monitor said Sunday.

Supported by regime ally Russia, Syria's army has waged a months-long offensive to recapture the vast desert region that stretches from the country's centre to the Iraqi and Jordanian borders.

On Saturday, "25 IS members were killed and others wounded in a commando operation by Syrian regime forces with air support from Russian warplanes and helicopters" in the northeast of Homs province, the Syrian Observatory for Human Rights monitoring group said.

Six members of the regime forces were also killed, it said.

A military source said the operation occurred "20 kilometres inside Daesh (IS) terrorist lines".

The raid allowed regime forces to seize control of three villages in the area, official news agency SANA reported the source as saying.

The army has captured swathes of territory from the jihadists in the province. According to the Observatory, IS now controls just dozens of villages in the east of Homs.

The Syrian "Badiya" is a large stretch of desert that extends over around 90,000 square kilometres (35,000 square miles) of territory.

Since 2015, much of the Badiya has been held by IS, but Syria's army has been chipping away at it since May.

Last week, the Observatory said regime forces had ousted IS from Al-Sukhna, the last jihadist-held town in Homs province.

Syria's army and Russia this weekend confirmed its full recapture.

"The liberation of Al-Sukhna from IS terrorists opens up possibilities for Syrian government forces to launch an assault and free the city of Deir Ezzor," a Russian army statement said.

The jihadists hold the majority of the vast desert province of Deir Ezzor including most of its provincial capital.

The recapture of Deir Ezzor "would largely -- if not completely -- mark the end of the fight against IS," Russia's Defence Minister Sergei Shoigu on Sunday told the Russia 24 television channel.

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Regime forces have more than doubled the territory they control in Syria over the past two months, he said.

Forces loyal to President Bashar al-Assad are also fighting the jihadists in the south of neighbouring Raqa province.

A US-backed Kurdish-Arab alliance meanwhile is battling to retake the provincial capital, Raqa city, from IS.

The jihadists also hold the majority of the vast desert province of Deir Ezzor including most of its provincial capital.

More than 330,000 people have been killed in Syria since the conflict erupted in March 2011 with anti-government protests.