BEIRUT (Reuters) - Kurdish forces in Syria said on Friday one of their fighters was mutilated by Turkey-backed rebels, referencing a video circulating on social media.

Turkey launched an air and ground offensive last month against Kurdish fighters who control the northwest Syrian region of Afrin on the Turkish border, opening a new front in Syria’s multi-sided war now approaching its eighth year.

The Kurdish-led administration of northeast Syria said Barin Kobane, a fighter with the Kurdish YPJ militia, was killed by Turkey-backed rebels who “played with her corpse and cut it up” as cameras rolled. The YPJ is the all-female affiliate of the Kurdish YPG militia.

“We hold the Turkish government responsible for this heinous act. We salute the soul of the free resistance (fighter),” it said.

Reuters could not immediately reach Turkish military officials for comment.

The footage showed a bloodied body on the floor. Parts of her torso appeared to have been cut.

The video has caused anger amongst the Kurdish population of northern Syria, a witness said. Memorial pictures of her are being circulated widely on social media.

The Syrian Observatory for Human Rights said she was killed during fighting in the north of the Afrin region near the Turkish border where Turkey-backed forces have taken some territory since launching its operation last month.

Kobane - her nom de guerre - was in her mid-twenties and joined the YPJ in 2015, a YPG official said. He said she was killed alongside three other fighters near the town of Bulbul.