The brother of a widely revered Shiite Muslim cleric in Saudi Arabia says a death sentence against the religious leader has been upheld on appeal.

Sheikh Nimr al-Nimr is a vocal critic of the government and was a central figure in Shiite protests that erupted as part of the Arab Spring. He was found guilty of sedition and other charges and sentenced to death in October last year.

His brother Mohammed al-Nimr said Sunday on Twitter that the sentence was upheld by an appeals court and the Supreme Court.

Saudi King Salman must still sign off on the sentence before it is carried out.

Al-Nimr's case attracted international attention, highlighting limits on free speech in the kingdom and tensions between the Sunni establishment and the Shiite minority.