An Egyptian court on Monday confirmed death sentences for 183 supporters of the outlawed Muslim Brotherhood on charges of killing police officers, as authorities continued a crackdown on opponents, AFP and Reuters news agencies reported.

The men were convicted of playing a role in the killings of policemen in the town of Kardasa in August 2013, during the upheaval that followed the army's toppling of Egypt's former President Mohamed Morsi.

In December the court issued its preliminary verdict against 188 defendants in a mass trial, of which two were acquitted on Monday while one was sentenced to 10 years in prison.

Charges against another two defendants were dropped after the court discovered that they were dead.

Monday's verdict came after the initial sentences were sent to the grand mufti, the government's official interpreter of Islamic law, for ratification.

The attack took place on the same day security forces violently dismantled two massive protest camps supporting Morsi in Cairo, killing hundreds of protesters in clashes.

The December verdict was the third mass death sentence of 2014, and was roundly condemned by rights groups.

"Mass death sentences are fast losing Egypt's judiciary whatever reputation for independence it once had," Sarah Leah Whitson, Middle East and North Africa director for Human Rights Watch, said at the time.

"Instead of weighing the evidence against each person, judges are convicting defendants en masse without regard for fair trial standards," she said.

In April 2014, Egyptians were shocked when a court passed down 683 death sentences in one trial.

In total, thousands of Brotherhood supporters have been arrested and put on mass trials in a campaign which human rights groups say shows the government is systematically repressing opponents.

President Abdel Fattah el-Sisi, who as army chief toppled Morsi, describes the Brotherhood as a major security threat.

The movement says it is committed to peaceful activism.