Syrian Kurds advances to Euphrates, despite Turkey's warning

Kurdish-led forces pushed into Syrian territory controlled by Islamic State fighters west of the Euphrates river on Sunday, defying a warning from Turkey.

The Syrian Observatory for Human Rights reported further advances by the Democratic Forces of Syria, DFS, after their capture Saturday of the strategic Tishreen Dam, which spans the river east of Aleppo, reports dpa.

The Hawar news agency, close to the Kurdish-led forces, said they were besieging "the remnants of the Daesh [Islamic State] mercenaries" in the town of Tishreen, west of the dam.

In October, Turkish Prime Minister Ahmet Davutoglu said his country's forces had opened fire upon the Kurdish People's Protection Units, the main component of the DFS, after they disregarded warnings not to cross the river.

Those incidents took place near the Turkish border, while the dam lies some 50 kilometres further south.

The area to the west of the Euphrates is controlled by Islamic State. It is the extremist group's last stretch of land adjoining the Turkish border after the Kurds, backed by US-led airstrikes, captured most of the border region over the course of this year.

The US envoy for the international coalition against Islamic State on Saturday described the dam at Tishreen as the group's "primary supply line into Raqqa," its de facto capital in Syria some 90 kilometres south-east along the Euphrates.

Turkey has been calling for the establishment of a safe zone in the area. It fears the expansion of the Kurdish forces, which are closely linked to Kurdish rebels operating on its territory.

Also on Sunday, the new leader of a powerful rebel group operating around Damascus called for the country's armed opposition to unite.

"Let's be united and join forces," Issam al-Boudani of the Army of Islam said in a video broadcast Sunday on Al Jazeera TV.

Al-Boudani, a field commander nicknamed Abu Hammam, took command of the rebel group on Friday, succeeding Zahran Alloush, who was killed in an airstrike near the Syrian capital Damascus.

"Victory will be attainable depending on how much we will be close to our religion," al-Boudani said.

Appearing clad in military fatigues, he also vowed that his group will go ahead with fight against al-Assad's regime.

"The mission of the Army of Islam is to restore the course of right and eliminate evil and its followers," al-Boudani, 40, said.

The Army of Islam controls the Eastern Ghouta region on the outskirts of Damascus, the main rebel stronghold in the region.

The faction was among several Syrian opposition groups that earlier this month attended a gathering in Saudi Arabia where they agreed to attend UN-sponsored peace talks with representatives of al-Assad's government. The meeting is planned for January.