An international relief organization says hospitals in the eastern side of Syria's Aleppo have been attacked 23 times since July, damaging all eight facilities that have not yet been shuttered or destroyed.

Doctors Without Borders, known by its French acronym MSF, said in a statement Friday that one of east Aleppo's two main surgical facilities has been out of service since Oct. 1. The organization supports eight hospitals across the city.

The U.N. estimates 275,000 people are trapped in a Russian-backed government siege of the city's rebel-held eastern districts, subjected to relentless bombardment.

"The situation is unbearable," said Carlos Francisco, MSF's head of mission to Syria. "The few remaining doctors with the capability to save lives are also confronting death."