DAMASCUS, Syria -- Islamic State militants on Saturday released 37 Syrian Christians, mostly women, who were among more than 200 people from the Assyrian minority group abducted in February, activists said.

Also Saturday, the Britain-based Syrian Observatory for Human Rights said the death toll from an airstrike on an IS-controlled eastern city near the border with Iraq rose to 71. The group initially reported that the Thursday attack killed 25 people.

The Observatory, which relies on a network of activists on the ground to monitor the war in Syria, said at least six children were among the dead. Other activist groups, as well as the Islamic State, said the attack was carried out by Russian jets, targeting a school and a popular market in Boukamal. In videos and pictures posted online purportedly showing the aftermath of the airstrike, people are seen digging for survivors in the rubble and holding children soaked in blood.

Russia began carrying out airstrikes in Syria on Sept.30, further complicating a civil war that is now in its fifth year. The conflict has killed 250,000 and displaced nearly half of Syria's pre-war population.

Suspected Russian airstrikes on Saturday hit Douma, a rebel-held town in the suburbs of Damascus, the Observatory said. It reported that 23 people were killed, including seven women and six children. The Syrian Civil Defence team in the suburbs of Damascus, a volunteer group of rescue workers, said 24 people were killed.

Russian officials deny their airstrikes have hit civilians, and say they focus their attacks on militant groups. Yet, the Observatory said it has recorded more deaths among civilians than militants since the Russian air campaign began.

The Assyrian Human Rights Network posted pictures on its Facebook page of the newly freed Christians arriving in the predominantly ethnic Assyrian village of Tal Tamr, in the northeastern Hassakeh province. The photos show a woman kissing the hand of an elderly woman in tears, and a priest greeting the former captives in a church ceremony.

The group said in a statement that negotiations continue for the release of another 124 people who remain in captivity.

Edmond Gabriel, chairman of the Assyrian Charitable Association in Hassakeh province, said 27 of the released are women. He said another group of captives was expected to be released Monday.

The Islamic State group shot and killed three Assyrians in October but has previously released others through negotiations.