BENGHAZI, Libya — Activists and medics say tribal clashes that erupted in southern Libya after three young men turned a pet monkey loose on a high school girl have killed at least 20 people.

The girl's family sought revenge after the monkey scratched and bit her last week, and killed all three men along with the animal.

Bader al-Daheli, a civil activist, said Sunday that the two main tribes in the southern city of Sabha, Awlad Suleiman and Gadhadhfa, are each backed by armed groups. Abdel-Rahman Areish, the head of Sabha hospital, said 20 people have been killed and 50 wounded.

Libya slid into chaos after the 2011 ouster and killing of longtime dictator Moammar Gadhafi. Much of the country is effectively ruled by a patchwork of local or tribal militias.