The Syria Democratic Forces (SDF) on Sunday announced the start of a campaign, dubbed "Euphrates Rage," to recapture what is regarded as IS' de facto capital, Raqqa. The US-backed, Kurdish-led Syrian movement is dominated by the main Syrian Kurdish fighting force, known as the People's Protection Units, or YPG.

SDF announced that the protection of civilians took priority in the operation, which it added would unfold "step by step." The majority of SDF fighters involved in the campaign are civilians who had previously managed to flee the city. A total of 30,000 were reported to be part of the offensive.

The announcement comes more than two weeks after US-backed Iraqi forces began a campaign to push IS militants out of their stronghold in neighboring Iraq, Mosul.

Turkish involvement?

The United States considers the Syrian Kurdish fighters as the most effective force against IS, but neighboring Turkey views them as a terror organization affiliated with the Kurdistan Workers' Party (PKK), which has fought a more than three decade long insurgency for Kurdish rights and autonomy. Turkey fears that the creation of an autonomous Kurdish region in Syria would fuel the aspirations of its own Kurdish population in southeastern Turkey and strengthen the PKK.

Turkey intervened in northern Syria on August 24 to clear IS from a section of the border and block the YPG from advancing further west. Dubbed "Operation Euphrates Shield," the military operation involves Turkish tanks, soldiers and artillery backed by US-led coalition airstrikes and ground forces from Turkey-backed rebels.

Turkey has said in the past that it would not accept a role for the Kurds in the liberation of Raqqa and that it might get involved in the conflict to prevent this from happening. Turkey's defense minister suggested that instead of the Kurds, Turkish-backed forces could present an "alternative."

An SDF commando leader reportedly told Turkey to stay out of the conflict, according to Germany's DPA news agency. Another SDF commander told a televised press conference that the group had "received international promises of providing military support for the al-Raqqa operation."

In a surprise visit to Ankara on Sunday, Chairman of the Joint Chiefs of Staff, US General Joseph Dunford, met with his Turkish counterpart Hulusi Akar, the Turkish military said in a statement. 

Raqqa is located about 100 kilometers (65 miles) south of the Turkish border. The city has been under IS control since 2014.

cw/ss/jlw (AP, Reuters, dpa)