BEIRUT (Reuters) - A car bomb planted by rebels linked to al Qaeda killed at least 26 people in Syria's northern city of Jarablus on Wednesday, most of them rival opposition fighters, the Syrian Observatory for Human Rights said.

Syria's rebel-held northern and eastern territories are mired in the worst episode of internecine clashes since the nearly 3-year-old uprising began, with hundreds killed in over a week of fighting between an alliance of rebel groups and an al Qaeda affiliated group known as the Islamic State of Iraq and the Levant (ISIL).

(Reporting by Erika Solomon; Editing by Mike Collett-White)