Updated

The Latest on the war in Syria (all times local):

4:30 p.m.

Syrian activists say a veteran Syrian opposition member who has been campaigning for the release of Syrian detainees has himself been detained.

The Syrian Observatory for Human Rights said Sunday Mohammed Saleh Abu Ali, in his 60s, has been detained at a checkpoint in the central city of Homs last Wednesday. A Facebook page for Syrian activists, Syrian News Activists, said Saturday he was detained from his home.

Syrian authorities don't comment on reports of detentions.

Abu Ali has been a government opponent since the 1980s, when he spent 12 years in prison as a member of the communist party. He was released in 2000, and was arrested again in 2015 for 17 months.

Abu Ali has been campaigning for the release of detainees. His detention comes amid a week-long hunger strike by hundreds in Homs' prison, calling for their release.

The Syrian Network for Human Rights, which tracks war detainees and casualties, has documented 85,000 Syrians that have been arbitrarily detained since the conflict began in 2011, 90 percent of them by the Syrian government which doesn't acknowledge their detention.

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3:20 p.m.

The U.S.-led coalition says allied fighters have captured Syria's largest oil field from the Islamic State group on Sunday, marking a major advance against the extremists in an area coveted by pro-government forces.

With IS in retreat, the Kurdish-led Syrian Democratic Forces and the Syrian government have been in a race to secure parts of the oil-rich Deir el-Zour province along the border with Iraq.

The SDF, with air support from the U.S.-led coalition, said Sunday it captured the Al-Omar field in a "swift and wide military operation." It said some militants have taken cover in oil company houses nearby, where clashes are underway. The U.S.-led coalition confirmed the SDF had retaken the oil field.

The Britain-based Syrian Observatory for Human Rights said pro-government forces retreated from the area around Al-Omar field after coming under heavy fire from IS. The SDF said government forces are three kilometers (two miles) away from the fields.