A U.S.-backed alliance of Syrian Kurds and Arab fighters says it has begun a battle to capture the Syrian city of Raqqa, the extremist group Islamic State's stronghold and self-declared capital in the country.
"We declare today the start of the great battle to liberate the city of Raqqa, the so-called capital of terrorism and terrorists," a spokesman for the Syrian Democratic Forces (SDF), Talal Silo, told journalists on June 6 in the village of Hazima, north of the city.
Silo said SDF forces were attacking the city from the north, west, and east, and urged civilians to keep away from Islamic State (IS) positions and the frontlines.
The British-based Syrian Observatory for Human Rights said the SDF has been engaged since dawn in heavy fighting with militants on the eastern and northern outskirts of Raqqa.
The observatory said the push followed heavy coalition air strikes overnight.
The U.S.-led coalition fighting IS in Syria and Iraq said the fight for Raqqa would be "long and difficult" but would deliver a "decisive blow to the idea of [IS] as a physical caliphate."
Coalition officials estimate that there are 3,000 to 4,000 IS fighters remaining in the city preparing for the assault.
The SDF has been gradually encircling Raqqa since November, and it remains unclear how many of its fighters have been deployed around the city.
IS militants seized large swaths of Syria and Iraq in an offensive in June 2014.
The offensive on Raqqa comes at a time when U.S.-backed Iraqi government forces say they are close to fully liberating Mosul, the final significant IS stronghold in Iraq.
'Dismantling The Caliphate'
The top commander of the international coalition, Lieutenant General Steve Townsend, said the coalition and its partners were "steadily dismantling the physical caliphate" of IS.
"It's hard to convince new recruits that [IS] is a winning cause when they just lost their twin capitals in both Iraq and Syria," he said.
The U.S.-led coalition has deployed special forces personnel to train and advise SDF forces on the ground and stepped up air strikes around Raqqa in recent weeks, leading to a rise in reported civilian deaths.
Last week, the United States announced it had begun providing weapons to members of the Kurdish militia that dominates the SDF, the Popular Protection Units (YPG).
The move has infuriated Ankara, which considers the militia an extension of the banned Kurdistan Workers Party (PKK) that has been fighting a decades-long insurgency in Turkey.
Turkish Prime Minister Binali Yildirim warned on June 6 that Ankara would respond if the offensive by the SDF poses a security threat to Turkey.
"To support terror organizations does not suit [our] alliance," Yildirim said. "We will immediately give the necessary response if we come across a situation in Raqqa or any other point in the region that threatens our security."