Amnesty on Hamas, reported in Guardian,

"As well as the unlawful killings, others abducted by Hamas were subjected to torture, including severe beatings with truncheons, gun butts, hoses and wire, or held in stress positions. Some were interrogated and tortured or otherwise ill-treated in a disused outpatients' clinic within the grounds of Gaza City's main al-Shifa hospital. At least three people arrested during the conflict and accused of collaboration died in custody."
http://www.theguardian.com/world/2015/may/27/hamas-executed-palestinians-under-cover-gaza-conflict-amnesty