The Islamic State (IS) terrorist group has claimed responsibility for the killing of a prominent Syrian anti-IS activist and his friend in Turkey.

IS issued a statement on November 2 saying it had "slaughtered" activist Ibrahim Abdul Qader and fellow activist Fares Hamadi in Sanliurfa, Turkey, on October 30.

Qader worked with the Raqqa Is Being Slaughtered Silently (RBSS) activist group to document atrocities committed by IS militants in the areas of Syria that they control.

"May every apostate know that he will be slaughtered silently," the IS video statement said.

The bodies of Qader and Hamadi were found in Hamadi's home by a friend on the morning of October 30, an RBSS spokesman said.

He noted that several RBSS activists had previously been killed in Syria, but this is the first time one has been killed outside the country.

Based on reporting by AFP and The Telegraph