Kurdish-led forces seized the Islamic State's main hub of Hajin Friday, a milestone in a massive and costly US-backed operation to eradicate the jihadists from eastern Syria.
The Syrian Democratic Forces secured Hajin, the largest settlement in what is the last pocket of territory controlled by IS, the Syrian Observatory for Human Rights said.
"After a week of heavy fighting and air strikes, the SDF were able to kick IS out of Hajin," Rami Abdel Rahman, the head of the Britain-based monitoring organisation, said.
The operation was completed at dawn, he said, a day after SDF forces fanned out across the large village in the Euphrates valley.
On Thursday, the last IS fighters were confined to a network of tunnels and the edges of Hajin, which lies in the eastern province of Deir Ezzor, about 30 kilometres (18 miles) from the border with Iraq.
The area held by IS is sometimes referred to as the "Hajin pocket", the last rump of a once-sprawling "caliphate" the group proclaimed in 2014 over swathes of Syria and Iraq.
IS fighters pulled back to positions east of Hajin Friday and to Sousa and Al-Shaafa, the two other main villages in their shrinking Euphrates valley enclave.
As recently as Thursday, the group posted pictures of fighting in Hajin on its social media accounts.
- High death toll -
According to Abdel Rahman, a total of 17,000 fighters from the Kurdish-Arab SDF alliance are involved in the operation to flush IS out of its last bastion.
The operation was launched on September 10 and has taken a heavy toll, according to figures collected by the Observatory, which has a vast network of sources on the ground.
At least 900 jihadists and 500 SDF fighters were killed in the fighting, the monitoring group said.
According to Abdel Rahman, more than 320 civilians were also killed, many of them in air strikes by the US-led coalition.
US President Donald Trump this week predicted the jihadist group would be fully defeated within a month.
"We've done a very, very major job on ISIS," he said on Tuesday, using another acronym for IS.
"There are very few of them left in that area of the world. And within another 30 days, there won't be any of them left," he vowed.
Western and other officials have repeatedly announced deadlines for a final victory over IS but the group is proving resilient.
- 30 days? -
The push to retake Hajin was delayed by Turkish threats on the Kurdish heartland further north and deadly counter-attacks by die-hard jihadists making a bloody last stand.
"ISIS anticipated its battlefield defeat and the loss of the caliphate and prepared accordingly," said Bruce Hoffman, a terrorism expert at Georgetown University in Washington.
Besides what is left of the pocket near Hajin in the Euphrates valley, IS has a presence in Syria's vast Badia desert, a front which is managed by Russian-backed government forces.
What is left of the jihadist group also has sleeper cells across Iraq and Syria that regularly carry out attacks.
The loss of Hajin came hours after IS's propaganda agency Amaq claimed responsibility for a Christmas market shooting in the French city of Strasbourg.
The Amaq statement was posted just after the shooter Cherif Chekatt was gunned down by police but bore the hallmarks of an opportunistic claim by the embattled jihadist group.