Beirut - Counter-attacks by Daesh have killed at least 47 US-backed fighters over two days as the extremists struck from their embattled holdout in eastern Syria, a war monitor said Saturday.

The Syrian Democratic Forces (SDF) Kurdish-led alliance supported by a US-led coalition is battling to expel the extremists from a pocket in the eastern province of Deir Al Zor on the Iraqi border.

The Britain-based Syrian Observatory for Human Rights monitor said the extremists launched “three separate assaults” on Saturday.

The monitor said the counter-attacks targeted the villages of Al Bahra and Gharanij and an area close to the Al Tanak oilfield, which is commercially active but is also an SDF military position.

SDF spokesman Mustafa Bali confirmed “a series of attacks” led Daesh IS in these three locations and said fighting had taken place all day, with the Kurdish-led ground forces receiving coalition air support.

The fighting on Saturday alone killed 29 SDF fighters, taking its total losses over the last two days to at least 47, said Observatory head Rami Abdul Rahman, revising up an earlier death toll of 24.

Thirty-nine Daesh extremists have been killed - some in the ground clashes, others in air strikes - over the same period, the Observatory said.

Daesh confirmed in a statement on Telegram that it had launched attacks near Al Bahra and Gharanij.

Earlier, the Observatory said Daesh had broken out of its holdout on Friday to attack Al Bahra, where SDF fighters and coalition advisers are based.

“Daesh launched a broad attack on the village of Al Bahra next to its holdout, taking advantage of the fog,” Abdul Rahman said.

The monitor said coalition raids have also killed 17 civilians, including five children, in the Daesh-held pocket since Friday.

Coalition spokesman Sean Ryan said he had not received any reports of civilian casualties, and insisted air strikes had been “very limited due to the weather”.

The anti-Daesh alliance has repeatedly denied previous reports of civilians killed in its air strikes, and said it does its utmost to avoid hitting non-combatants.

Deir Al Zor activist Omar Abu Leila said the attack on Al Bahra was “very scary” and that Daesh fighters were able to move quickly “taking advantage of the fog”.

Daesh overran large swathes of Syria and neighbouring Iraq in 2014, proclaiming a “caliphate” in land it controlled but has lost most of it to offensives by multiple forces in both countries.

In Syria, the extremists are largely confined to the pocket in Deir Al Zor, but they also have a presence in the vast Badia desert that stretches across the country to the Iraqi border.

Since 2014, the US-led coalition has acknowledged direct responsibility for over 1,100 civilian deaths in Syria and Iraq, but rights groups put the number much higher.

Syria’s war has killed more than 400,000 people and displaced millions since it started in 2011 with the brutal repression of anti-government protests.