A US-backed militia alliance has begun what it says is the final stage of a campaign to clear the Islamic State (IS) group from north-eastern Syria.
The Syrian Democratic Forces launched a ground offensive on Monday against jihadist militants around Hajin, a town in the Middle Euphrates River Valley.
The international coalition backing the Kurdish and Arab fighters said they were expecting a “difficult fight”.
Most are believed to be in an area stretching east from the Euphrates to the border with Iraq, about 25km (16 miles) away from Hajin, and in desert areas in the south and centre of the country, where the Syrian government is battling them.
Between 15,500 and 17,100 militants are thought to be based in Iraq, where IS no longer fully controls any territory. Many are hiding in the vast western desert.
At its peak in 2014, IS established a “caliphate” stretching across Syria and Iraq that was similar in size to the UK and ruled over more than 7.7 million people.
SDF fighters launched the operation to drive IS “remnants” out of Hajin and the remaining countryside of eastern Deir al-Zour province after clearing the Baghuz and Dashisha areas – to the north and south – over the past four months.
An unnamed SDF commander told AFP news agency that at least 15 IS militants were killed in the first day of the Hajin offensive.