Iraqi Special Operations Forces (ISOF) inspect weapons of lslamic State militants during an operation to clear the al-Andalus district of Islamic State militants, in Mosul, Iraq, January 16, 2017. USA -led coalition warplanes pounded Islamic State positions in the area.
The SDF has said it will hand control of Raqqa to a civilian council from the city after its capture, echoing the pattern in other areas retaken by the SDF.
Yesterday, the Observatory claimed an air strike had struck and killed 21 civilians as they fled the city across the Euphrates on a dinghy. The PYD is the political arm of the YPG.
Late last month, US Army Colonel Ryan Dillon, the spokesman for the anti-IS operations, tweeted Americans would not put a timeline but support partner forces when they start attacking Raqqa.
The commander of the Raqqa campaign, Rojda Felat, confirmed an assault had begun on the Al Mashlab district at the city's southeastern outskirts. "The advance came after heavy air strikes by the US-led coalition", he told AFP.
"We all saw the heinous attack in Manchester, England".
"Regime forces entered Raqa province for the first time in a year, coming from Aleppo province" to the west, the Syrian Observatory for Human Rights monitor said.
Turkey is unhappy that the USA has armed Kurdish fighters with heavier weapons in the battle for Raqqa.
The US-led coalition quickly reported the launch of the battle on its website, calling the battle against the Islamic State in Raqqa a "blow to the idea of a physical caliphate".
This "may indicate ISIS intends to use the 200,000 people still trapped in the city as human shields", the aid group said, using another acronym for IS.
The city is about 90km from the border with Turkey.
Syria's state news agency SANA reported on Monday that at least seven civilians were killed in rocket attacks by the rebels in a Deraa suburb just 4km east of Deraa city.
It said civilians had been escaping Raqa by crossing the Euphrates River via boat, after the two main bridges leading out of the city were destroyed.
More than 320,000 people have been killed and millions more have fled their homes since the civil war erupted in Syria in March 2011.