US-backed Syrian forces seize dam west of Raqqa from IS

US-backed Syrian militias said they seized a major dam on the Euphrates river from the Islamic State group on Sunday, their latest gain as they push towards Raqqa city.

The Syrian Democratic Forces, an alliance of Kurdish and Arab fighters, said they captured the Baath Dam in the morning, renaming it Freedom Dam. The hydroelectric dam lies some 22 km upstream of Raqqa, where IS's main base of operations is in Syria.

The spokesman for the Kurdish YPG militia, the SDF's key component, said fighters were combing nearby villages for mines and shoring up their defensive lines. "The dam has been completely liberated," Nouri Mahmoud said.

The advance means the SDF now hold all three major dams along the Euphrates, after gaining control of Syria's largest dam last month.

With air strikes and special forces from the US-led coalition, the SDF has been encircling Raqqa to take the city, which Islamic State has used as a hub to plan attacks abroad.

The alliance advanced in recent months to within several kilometres of the centre of Raqqa, facing fierce resistance from IS. Fighting since late last year has displaced tens of thousands of people, according to United Nations sources, with many flooding camps in the area.

The operation to storm the city will start in the next "few days," Mahmoud had said on Saturday. The Raqqa assault will pile more pressure on the militant group's self-declared "caliphate" as it faces defeat in the Iraqi city of Mosul and retreats across much of Syria.

But Mahmoud's comments were directly contradicted by Turkish Prime Minister Bin Ali Yildirim who told Turkish journalists that the operation to take control of Raqqa began two days ago. 

"The long-planned Raqqa operation began late on June 2," after the US informed Turkey of the operation, Yildirim said, without providing further details, according to the Anadolu news agency. 

The Raqqa operation has been a deep source of tension between Washington and Ankara because of US support to YPG, which has included air cover, assistance from special forces on the ground and weaponry.

Arming the Kurds

The US said last week it began sending arms to Kurdish fighters, which Turkey said was "extremely dangerous" and urged Washington to reverse the decision.

Washington views the YPG as the most effective fighting force against IS.

But Yildirim said its NATO ally had downplayed its support for YPG, referring to the relationship as a "tactical cooperation," according to comments reported by Anadolu Sunday.

In April, Turkey announced the completion of its half-year Euphrates Shield operation in northern Syria against both extremists and Kurdish militia.

But during his briefing with journalists on Saturday evening, according to Anadolu, Yildirim suggested Turkey would not shy away from further action, without giving further detail.

"Whether inside or outside the country, we will not hesitate or hold back from taking the necessary steps for the security of our country and people," Anadolu quoted him as saying.

"We've done this in the past and after this if it is required, we would do so again," Yildirim added.

IS militants still control swaths of Syria's eastern deserts bordering Iraq and most of Deir el-Zor province, which would be their last major foothold in Syria if they lose Raqqa.