People gather around a hole left by an airstrike carried out by the Saudi-led coalition in Sanaa, Yemen, on April 28, 2018. (File Photo: Xinhua)

SANAA, Sept. 1 (Xinhua) -- At least 50 prisoners of war were killed when the Saudi-led coalition launched a series of airstrikes overnight on a prison in Yemen's central province of Dhamar, the Houthi-controlled health ministry said in a statement early Sunday morning.