An alliance of Arab and Kurdish fighters seized more than a dozen villages in eastern Syria on Tuesday in their drive to encircle the Islamic State group bastion of Raqa. 

The US-backed Syrian Democratic Forces (SDF) made a major incursion into the oil-rich province of Deir Ezzor as part of their push for Raqa, field commander Dejwar Khabat said. 

"Our aim is to cut the road to Raqa and besiege IS... We have liberated 15 villages," Khabat said Tuesday in the town of Makmaneh, which lies on a major highway approximately 100 kilometres (60 miles) east of Raqa city. 

He said the IS was dispatching suicide bombers but had not been able to slow the offensive. 

SDF fighters on Tuesday set up their base on a hilltop in Makmaneh, digging trenches around it to prevent suicide bombers or car bombs from reaching them.  

Backed by air strikes from the US-led coalition, the SDF has seized swathes of territory in northern Syria from the jihadists. 

It launched its offensive for Raqa -- the de facto Syrian capital of IS's so-called caliphate -- in early November.

Deir Ezzor province lies just east of Raqa, and is almost completely held by IS. The jihadists also hold most of the provincial capital by the same name, and have been battling regime forces to overrun the city. 

The SDF alliance is dominated by the Kurdish People's Protection Units (YPG), but it also boasts several units of Arab fighters. 

"We have entered the first villages of Deir Ezzor province," said Abu Khawlah, who heads the 1,700-strong Deir Ezzor Military Council, an Arab component of the SDF. 

"Our entry into Deir Ezzor was a big surprise (for IS), and thre will be more surprises coming," he said. 

The SDF, which has been lobbying for weapons to help them carry out the offensive, has recently received armoured SUVs from the United States.

A US-led coalition has been carrying out air strikes on IS in Syria and neighbouring Iraq since 2014.The Syrian Observatory for Human Rights said Tuesday's advance was the SDF's "biggest incursion" yet into Deir Ezzor province. 

It also reported 11 people killed on Tuesday in unidentified air strikes on a gas station and parking garage in an IS-held village in the province.  

"The death toll could rise because there are at least 35 people wounded, some of them in critical condition," monitor head Rami Abdel Rahman said. 

He could not specify which airplanes had carried out the bombing raids.

The province has been targeted in the past by both the US-led coalition and regime ally Russia, who has been waging an air war in support of Syrian President Bashar al-Assad since September 2015. 

More than 310,000 people have been killed since Syria's conflict erupted in March 2011 with protests calling for Assad's ouster. 

source: AFP