A Cairo court has convicted a leading Muslim Brotherhood figure and two other Islamists and sentenced them to 15 years in prison each on charges of torturing a man during the 2011 protests against then-President Hosni Mubarak.

State MENA news agency says the court on Saturday found Mohammed el-Beltagy along with a preacher and a junior member of the group guilty of holding and beating a man in an office overlooking Tahrir square they suspected was an undercover policeman spying on the 18-day sit-in against Mubarak.

El-Beltagy was a regular speaker at the sit-in, which eventually led to the ouster of the longtime autocrat.

El-Beltagy has already been sentenced to 20 years for allegedly torturing two police officers during last summer's protest against the ouster of Islamist President Mohammed Morsi.