CAIRO—An Egyptian court re-opened a sensitive political wound Sunday when it overturned former President Hosni Mubarak's life sentence over his role in the deaths of hundreds of protesters during the country's revolution two years ago, and ordered a retrial.

The judge also ruled to retry Mr. Mubarak's interior minister, Habib Al Adly, who is also serving life in prison, and reopened murder and corruption trials for nine co-defendants who had been acquitted: six of his top security officers, a former Mubarak business partner...