An Egyptian court has confirmed the death sentences of more than 180 Islamists, including the top leader of the Muslim Brotherhood.

Lawyers say the ruling can be overturned on appeal. It was not immediately clear how many sentences had been confirmed, with lawyers giving estimates ranging from 182 to 197.

Lawyers boycotted the opening of the trial on March 25 to protest against an earlier mass death sentence by the judge. A month after that session, the judge sentenced 683 people to death, including the Muslim Brotherhood's supreme guide Mohammed Badie.

The case is rooted in retaliatory attacks on a police station in the southern city of Minya on August 14, after police dispersed an Islamist sit-in in Cairo, killing hundreds.

Of the 683, all but 110 were tried in absentia, according to defence lawyer Khaled el-Komi.

Death sentences issued for those in absentia are automatically cancelled in Egypt if they turn themselves in or are apprehended, and a retrial is ordered.

The death sentences have sparked international condemnation and raised questions about the independence of the judiciary.

Mohammed Tosson, representative of the defence team, said that 183 people were sentenced to death, four received life sentences and 496 were acquitted. Those sentenced to death include a Coptic Christian and a blind man, said another lawyer, Mohammed Abdel-Wahab.

The charges ranged from sabotage and terrorising civilians to murder.

This is the second death sentence against Badie, who faces multiple charges linked to the violence that engulfed the country after the ousting of former president Mohammed Morsi. The military forced Egypt's first democratically elected leader from power last July after massive protests demanding his resignation.