Islamic state militants reportedly tortured and then publicly killed a human rights lawyer in the Iraqi city of Mosul after their self-proclaimed religious court ruled that she had abandoned Islam.

Huffington post reports that according to the U.N. mission in Iraq, some armed ISIS men seized Samira Salih al-Nuaimi, a human rights lawyer in a northeastern district of the Mosul while she was home with her husband and three children.

According to reports from The Associated Press, Al-Nuaimi was taken to a secret location. After about five days, the family was called by the morgue to retrieve her corpse, which bore signs of torture, the two people said, speaking on condition of anonymity because of fears for their safety.

The United Nations Assistance Mission in Iraq say her arrest was allegedly connected to Facebook messages she posted that were critical of the militants' destruction of religious sites in Mosul. A statement by the U.N. on Thursday added that al-Nuaimi was tried in a so-called "Sharia court" for apostasy, after which she was tortured for five days before the militants sentenced her to "public execution." Her Facebook page appears to have been removed since her death.

Nickolay Mladenov, the U.N. envoy to Iraq, said in a statement, referring to the group by an acronym.

The statement did not say how she was killed.

Among Muslim hard-liners, apostasy is thought to be not just conversion from Islam to another faith, but also committing actions that they believe are so against the faith that one is considered to have abandoned Islam.