The medical charity Doctors Without Borders is condemning the latest attack on one of its clinics in South Sudan.

The aid group also known by its French acronym MSF says the armed robbery by several men in Pibor injured two team members early Thursday and forced some staffers to relocate. Some workers were threatened with guns, and office equipment was stolen.

A separate statement by the U.N. peacekeeping mission in South Sudan says peacekeepers early Thursday rescued more than a dozen aid workers in Pibor who came under "heavy fire from unknown gunmen." The statement says about 40 attackers were involved and the aid workers were evacuated from the compound unharmed.

Aid workers have faced widespread insecurity amid South Sudan's civil war, which is well into its fourth year.