Four men have been sentenced to death by hanging in Afghanistan for killing a woman accused of burning the Quran.

Eight other people received 16 year sentences for the killing in the verdicts given on 6 May, and 18 were found not guilty.

The woman, known by the single name Farkhunda as is Afghan custom, was filmed being brutally beaten, kicked and stoned by a mostly male mob in Kabul, before being thrown off a bridge, set on fire and thrown into a river.

The murder of the 27-year-old provoked mass protests in Kabul, with crowds demanding that authorities do more to uphold women's rights.

Judge Safiullah Mujadidi said the sentences in the cases of 19 police officers charged in connection with the killing would be announced next week.

Initial reports after the murder suggested that Farkhunda was mentally ill, but her family said that their daughter was a religious teacher, who taught the Quran to children, and would never destroy a copy of the religious text.

They allege that the imam of a local mosque made the false accusation after she accused him of spreading false tawiz, or Quranic verses worn as pendants to bring luck.

An incensed crowd then attacked the woman.

"We were asking the people to stop beating her and let us ask what religion she belongs to," one witness told CNN affiliate TOLOnews. "But the people didn't listen to us and kept beating her."

Afghanistan's Ministry of Hajj and Religious Affairs said it had found no evidence Farkhunda had burned the Quran.