Question: At what prison did extrajudicial executions occur according to HRW?
Sentence: Opponents were critical of Libya's human rights abuses; according to Human Rights Watch (HRW) and others, hundreds of arrested political opponents often failed to receive a fair trial, and were sometimes subjected to torture or extrajudicial execution, most notably in the Abu Salim prison, including an alleged massacre on 29 June 1996 in which HRW estimated that 1,270 prisoners were massacred.
Answer in sentence: yes