CAIRO (AFP, Reuters) - An Egyptian court on Monday confirmed death sentences against 183 supporters of the outlawed Muslim Brotherhood convicted of killing 13 policemen in a town near Cairo in August 2013.

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

Charges against the remaining two 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 accused, of whom 143 are behind bars, were found guilty of taking part in an August 14, 2013 attack on a police station in Kerdassa, a village on the outskirts of Cairo, in which 13 policemen were killed.

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

Since the army deposed Morsi on July 3, 2103, at least 1,400 people have been killed in a police crackdown on protests.

Hundreds were sentenced to death in swift mass trials which the United Nations says were "unprecedented in recent history".