( CNN ) ISIS militants in northern Syria released 19 Assyrian Christian hostages on Sunday , according to Rami Abdelrahman , the chief of the London-based Syrian Observatory for Human Rights . Abdelrahman has a network of activists on the ground in Syria . On Saturday , the observatory -- citing an Assyrian commander -- said that ISIS planned to release 29 Assyrian Christian hostages . ISIS captured at least 220 Assyrians , all Christians , on February 23 during an attack on the villages around the town of Tal Tamer in the northern Syrian province of al-Hasakah . The Syrian Observatory said Saturday that a self-proclaimed ISIS court ordered the release , citing an Assyrian commander . The `` court '' told the commander that the fate of the other kidnapped Assyrians has yet to be decided by ISIS Sharia jurists . The Syrian Observatory said its information indicates ISIS has taken the hostages to the Mount Abdelaziz area , southwest of Tal Tamer . The founder of the Assyrian Human Rights Network , Osama Edward , puts the number of Assyrian hostages at more than 262 . Edward is based in Sweden but has family in the area that was attacked , and says his information is from the network 's team on the ground . The number of hostages has climbed steadily , from an initial estimate of between 70 and 100 people seized on Monday to 150 as of Wednesday , with women , children and the elderly among them . The number of people executed by the terrorist group has also climbed steadily . Since the declaration of its `` caliphate '' last June , ISIS has killed 1,969 people , the Syrian Observatory said Saturday . Nearly two-thirds of them -- 1,238 people -- were civilians . Six were children and eight were women , the group said . Of the rest , 95 were fighters from the al Qaeda-affiliated rebel group al-Nusra Front , the Syrian Observatory said , and 511 were officers and soldiers of regime forces . ISIS also executed 125 of its own members for `` exceeding the limits in religion , '' the Syrian Observatory said . `` We in SOHR believe that the real number of people that had been killed by ( ISIS ) is higher than the number documented by SOHR because there are hundreds of missing and detainees inside the ( ISIS ) jails , loss of communication with about 1,000 men of al-Shaitaat tribe , ( and ) dozens of Kurds who have still been missing '' since ISIS attacked the Syrian town of Kobani in September . CNN 's Samira Said in Abu Dhabi and Hamdi Alkhshali in Atlanta contributed to this report .
ISIS captured Assyrian Christians in various villages in northern Syria . ISIS has executed 150 people since June , the Syrian Observatory reports .