At least 65 ISIS fighters have been killed around their last enclave in Syria despite a pause in a two-month Kurdish-led assault, a monitor said on Wednesday.
The US-backed Syrian Democratic Forces announced a pause in its offensive in eastern province Deir Ezzor last week in protest at Turkish shelling of Kurdish positions along Syria's northern border.
But waves of US-led air strikes since Monday have killed 48 extremists, including during two ISIS assaults on oilfields north of the Hajin enclave, the Syrian Observatory for Human Rights said.
On Tuesday, ISIS fighters launched an assault on the Azrak oilfield, followed by an attack on Wednesday on the Tanak oilfield where US-backed SDF fighters are based, it said.
A coalition spokesman did not immediately reply to a request for comment.
The SDF killed another 17 ISIS fighters while defending a base in the village of Al Bahra just outside ISIS-held territory on Monday, the UK-based monitoring group said.
Alliance spokesman Kino Gabriel had stressed that the pause in offensive operations did not mean SDF fighters would not defend themselves.
The SDF launched its assault on the ISIS enclave around Euphrates valley town Hajin on September 10.
But after making slow progress, it suffered a major setback last month when ISIS used cover provided by sandstorms to launch a series of counter-attacks.
By the end of the month, the extremist group had recaptured all of the territory the SDF had won.
The Hajin enclave is the last significant remnant of the "caliphate" ISIS proclaimed in 2014 across a vast area of Syria and neighbouring Iraq.
The rest has all been lost to offensives by multiple alliances on both sides of the border.
Outside the Hajin enclave, the group's operations are confined to sleeper cells and to hideouts in unpopulated desert and mountain areas.
The observatory relies on sources inside Syria for its information, and says it determines who carried out strikes based on aircraft and munitions used, locations and flight patterns.
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