The commander of the Kurdish-led Syrian Democratic Forces (SDF) said on Sunday a "successful operation" resulted from joint intelligence work with the United States, in an apparent reference to reports that Islamic State leader Abu Bakr al-Baghdadi is believed to have been killed in a U.S. military operation in Syria. "An historic, successful operation as a result of joint intelligence work with the United States of America," Mazloum Abdi said on Twitter.