Hayat Tahrir al-Sham, whose name means Organization for the Liberation of the Levant, was the main rebel group leading the latest offensive, launching a surprise assault in late November from northwestern Syria that quickly led to the fall of President Bashar al-Assad. It is now leading the transition to a new Syrian government.

The news comes a day after Syria’s new interim leader Mohammed al-Bashir announced he was assuming the role of the country’s caretaker prime minister until March 1. Bashir previously served as the head of the rebel administration’s self-formed “salvation government.