Islamic State jihadists have reportedly slaughtered up to 280 people in the Deir ez-Zor province, killing “whole families” for alleged cooperation with the Syrian troops. The killings are said to have taken place a day after Russian humanitarian aid was airdropped in the region.

Local residents told Sputnik news agency the massacre happened in al-Bagilya settlement, an area which received Russian airlifted aid earlier.

“The horrific massacre carried out today by ISIL militants in al-Bagilya in Deir ez-Zor. 280 victims, including women, children and old people. Reason – cooperation with the Syrian army,” a Sputnik source said.

Islamic State (IS, previously ISIS/ISIL) militants reportedly carried out executions of “whole families.”

Jihadist beheading plot inspired by ‘chilling’ fatwa http://t.co/LheIo9gnuxpic.twitter.com/TuLZ3ENPt6 — RT UK (@RTUKnews) October 12, 2015

Previously, reports indicated that IS fighters were moving their way up to the northern part of the Deir ez-Zor province.

The massacre appears to be one of the worst daily mass killings that took place over the five years of the Syrian conflict.

Syrian state media reports that all the people killed were civilians. But local monitoring groups say dozens of government troops were killed as well.

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Syrian state news agency SANA initially reported that IS fighters murdered dozens of civilians, without providing any further details. Meanwhile, the Lebanon-based Al-Mayadeen TV said that 280 people were killed, including children and women. The TV channel added that the dead bodies were dumped in the Euphrates River, while 400 survivors were taken hostage.

Reuters also reported at least 250 people dead in Bagilya settlement, citing a source close to the government. Some of the victims were beheaded, according to the source.

READ MORE: ISIS kills 400, mostly women & children, in Palmyra – Syrian state TV

Hours after the attack was reported, the governor of Deir ez-Zor province, Mohammad Qaddur Ajnyyja, told Sputnik that Syrian army has successfully freed the settlement from Islamic State control.

“ISIL militants entered in the village of al-Bagilya… last night and perpetrated a massacre of whole families. For this reason the army headed to this region to save the population. There were clashes with ISIL militants, they suffered significant casualties, the rest succeeded to flee to the neighboring areas controlled by ISIL,” Ajnyyja said.

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RT has requested information on the atrocity from several organizations on the ground, including the Red Cross, and is following the developments.