US-Backed Syrian Group Attacks IS Near Raqqa
It comes as Iraqi troops continued their major offensive against the jihadists in the city of Fallujah for a second day.
They are among the most serious ground operations against IS since the militants declared their self-styled 'caliphate' covering large areas of Syria and Iraq in 2014.
The assault in RaqqaÂ province by the Syrian Democratic Forces (SDF) was aimed at pushing IS from the northern part and securing other areas.
The SDF, backed by the US, is a seven-month-old alliance of Syrian militias, including the Kurdish YPG.
With the help of American-led coalition airstrikes, the YPG has driven the jihadist organisation from large areas of northern Syria in the last year.
Syrian activists claim IS fighters are using civilians as human shields in Raqqa - but there has been no indication of when a full assault on the predominently Arab city might take place.
Syrian Kurdish groups have said an attack there should be led by Arab militias. However, some experts claim they are not yet ready for such an operation.
Abdel Aziz al Hamza, a co-founder of the Raqqa is Being Slaughtered Silently group, said: "They are using the civilians as a cover. So you'll find them in the same building.
"In a civilian building, you'll find two or three apartments for ISIS fighters.
"They also talk of some schools as places to stay because these schools have basements, something underground, so they are protected from the air strikes. And they are surrounded by civilian buildings."
Meanwhile in Fallujah, a resident speaking by phone said there was heavy shelling on the northern edge of the city.
The man said: "Daesh (IS) is still imposing a curfew, preventing people from coming out on the street."
The Raqqa province operation took place along with coalition airstrikes on militant hideouts in the area.
And the assault followed a visit to Syria by US Central Command Commander General Joseph L Votel , the highest-ranking US military official to go there since the conflict began in 2011.
Mr Votel said local forces being trained by US special forces were proving to be "capable and competent partners".
He added: "They're exhibiting their initiative, their innovativeness, their skills, their expertise to really make a difference here."
Washington's strategy in Syria has changed from trying to train thousands of fighters outside the country to supplying groups whose commanders have been vetted by the US.
The delivery of weapons since the alliance was set up has helped the SDF fighters push further south into Islamic State-held territory, say American officials.