CAIRO (AP) — Egypt’s former autocratic president Hosni Mubarak, who was forced to step down following 2011 mass protests, has undergone surgery, his eldest son tweeted Friday.

Alaa Mubarak tweeted that his 91-year-old father was operated on Thursday and that his condition was “stable.” He provided no details about the surgery.

Mubarak was ousted in the 2011 uprising that swept Egypt as part of the Arab Spring movement that gripped the region. He was sentenced to life imprisonment for involvement in the killing of anti-government protesters but later retried and subsequently acquitted and released in 2017. Mubarak’s two sons, Alaa and Gamal, were both convicted and served prison terms for corruption.

Since their release, Mubarak’s family has remained in Egypt, where they have kept a low profile but still enjoy special treatment under former general and current president Abdel Fattah el-Sissi. El-Sissi led the military overthrow of elected but divisive Islamist president Mohamed Morsi, Mubarak’s immediate successor.