BEIRUT (Reuters) - An American man who died fighting alongside Syrian Kurdish fighters to oust Islamic State from the northern Syrian city of Manbij has been named as Levi Jonathan Shirley.

Shirley, who adopted the Kurdish name of Agir Servan, was killed on July 14, the Kurdish Peoples' Protection Units (YPG) said in a statement posted on its website on Thursday.

The YPG is part of a U.S.-backed alliance of Syrian Kurdish and Arab fighters called the Syria Democratic Forces (SDF), which launched an offensive in May to seize the last territory held by Islamic State insurgents on Syria's frontier with Turkey.

The YPG has attracted foreign fighters from around the world, including Britain, Germany, Canada, Australia and Turkey. A YPG official said in February that seven Westerners had died fighting with the group.

In May, the YPG said a Portuguese national had died, also fighting in Manbij.

The SDF has largely avoided fighting forces allied to Syrian President Bashar al Assad and has focused on battling the hardline Islamic State militants in Syria's five-year-old conflict.

(Reporting by Lisa Barrington; Editing by Catherine Evans)