Extremists within the Islamic State group publicly killed a rights lawyer in the Iraqi city of Mosul after their self-styled Islamic court decided that she had abandoned Islam, The Washington Times reported Thursday.

Samira Salih al-Nuaimi was nabbed from her home on Sept. 17 after allegedly posting messages on Facebook that criticized the militants' destruction of religious spaces in Mosul.

Al-Nuaimi was tried in a so-called "Sharia court" for apostasy, followed by five days of torture before the militants sentenced her to "public execution," according to the United Nations Assistance Mission in Iraq.

She was killed on Monday, the U.N. mission said. Her Facebook page appears to have been taken down after her killing.

Among strict Muslims, apostasy is believed to be not just conversion from Islam to another faith, but also committing actions that they feel are so counter to the faith that the perpetrator is considered to have abandoned Islam altogether.

Mosul is the largest city held by the Islamic State group in the self-declared "caliphate" it has carved out, bringing together northern and eastern Syria with northern Iraq. Since taking over the once-diverse city in June, ISIS has forced religious minorities to convert to Islam, pay special taxes or die, causing tens of thousands to flee. The militants have also enforced strict dress codes for women and have even veiled the faces of female mannequins in store fronts, according to ABC.

Al-Nuaimi's death is the latest in a series of attacks by ISIS to silence female activists and politicians. In the nearby town of Sderat, militants broke into the home of a female candidate in the last provincial council elections, killed her and abducted her husband, the U.N. said in July. Another female politician was abducted from her home in eastern Mosul on the same day; she is still nowhere to be found.