Islamic State fighters have seized a Syrian army base in the northern province of Raqa, killing scores of troops and beheading some of them, a monitoring group says.
The takeover of the base of Division 17 came as the UN Commission of Inquiry on Syria said on Friday that IS fighters accused of atrocities would be added to a list of war crimes indictees.
In the two-day assault on the base in Raqa province, an IS bastion, the jihadists killed at least 85 soldiers, the Syrian Observatory for Human Rights said on Saturday.
More than 50 troops were summarily executed, 19 others were killed in a double suicide bombing and at least 16 more died in the assault launched early on Thursday.
Hundreds of troops "withdrew on Friday to safe places - either to nearby villages whose residents oppose IS or to nearby Brigade 93 - but the fate of some 200 remains unknown," Observatory head Rami Abdel Rahman said.
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"Some of the executed troops were beheaded, and their bodies and severed heads put on display in Raqa city," an IS stronghold, he told AFP.
Video shot by jihadists and distributed on YouTube showed IS fighters apparently inside Division 17 living quarters burning a portrait of Syrian President Bashar al-Assad.
The jihadists also posted photographs online of the bodies of decapitated soldiers strewn across the ground.
