Egypt's Parliament has begun voting over constitutional amendments to allow President Abdel-Fattah el-Sissi to stay in power, possibly until 2034, and further enshrine a role for the military in state affairs.

The voting was announced on state media on Thursday, after three rounds of discussions among lawmakers that started the previous day, although the 596-seat chamber is packed with el-Sissi loyalists.

The amendments are almost certain to pass, allowing el-Sissi 12 more years after his second term expires in 2022.

Once passed, amendments must be finalised by a special legislative committee for a final decision within two months, followed by a nationwide referendum, likely before early May.

Critics of the move argue Egypt is slipping back into authoritarianism, eight years after a pro-democracy uprising ended autocrat Hosni Mubarak's three-decade rule.