At least seven fighters from a Kurdish-led force were killed Sunday in two Islamic State group attacks in eastern Syria, a war monitor said.

"Six fighters from the Syrian Democratic Forces (SDF) were killed" in an attack along the road linking Deir Ezzor province with Hasakeh, said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

A seventh was shot dead by gunmen in the west of Deir Ezzor province, the Observatory said.

The attacks were carried out in areas under the control of the SDF, which is a key U.S. partner in fighting IS and is the Syrian Kurds' de facto army.

On Thursday, the SDF said two of their fighters were killed and six arrested following clashes in a volatile Syria camp where a security operation was under way.

Syria's war began in 2011 and has killed nearly half a million people and forced around half of the country's pre-war population from their homes./agencies