A US-backed Kurdish-led alliance announced Tuesday it is launching the final stage of its battle to expel the Islamic State jihadist group from its desert holdouts in eastern Syria.
Backed by the US-led coalition, the Syrian Democratic Forces have driven the jihadists out of large parts of the country.
But IS fighters have retained a presence in a few parts of the country, including in the eastern oil-rich province of Deir Ezzor near the border with Iraq.
The SDF's Deir Ezzor Military Council on Tuesday said it would press its efforts to oust IS from remaining areas.
"Our forces with the forces of the international coalition have started the last stage" of the anti-IS campaign, it said in a statement.
IS holds dozens of villages in eastern Syria, from the eastern banks of the Euphrates River that cuts across Deir Ezzor to the border with Iraq, and in the south of the adjacent province of Hasakeh.
"Our forces will liberate these areas and secure the Iraqi border once and for all," the military council announced at the Al-Tanak oilfield east of the Euphrates.
In a separate offensive, Russia-backed Syrian regime forces have expelled IS from areas to the west of the Euphrates including the provincial capital of the same name.
Deir Ezzor Military Council head Ahmed Abu Khawla told AFP there was a "shared operations room with Iraqi forces".
The US-led coalition including French forces had increased their numbers and would support the SDF in "the final stage" of their operation, he said.
French special operations forces arrived in Syria last month to help boost US-led efforts against IS, US Defence Secretary Jim Mattis said last week.
IS jihadists swept across large parts of Syria and neighbouring Iraq in 2014, declaring a so-called "caliphate" in areas they controlled.
But the jihadists have since lost much of that territory to various offensives in both countries.
In Syria, regime forces are also battling IS in the southern suburbs of the capital including the neighbourhood of Yarmuk.