A group of U.S.-trained Syrian rebels have declared their refusal to fight al-Qaeda’s affiliate in the country, the Nusra Front, following a series of kidnappings by the militant group,The Guardian reported on Thursday.

Citing a source in Division 30, a group believed to have been trained by U.S.-backed forces, the British newspaper said the rebels also oppose U.S. airstrikes against al-Nusra Front.

In late July, al-Nusra Front vowed to cut off “the arms” of the American government in Syria when they attacked headquarters of Division 30, killing at least five fighters.

Al-Nusra Front detained the rebel group’s commander Col. Nadim al-Hassan along with six others last week.