CAIRO — An Egyptian appeals court on Sunday overturned the conviction and life sentence of former president Hosni Mubarak for directing the killing of hundreds of protesters, a ruling that could prolong a politically fraught legal battle over the fate of the dictator two years after his ouster.

The court ordered a new trial for Mubarak and his former security chief, Habib el-Adly, who was convicted and sentenced to life in prison on the same charges.