This combination of satellite images made on Sept. 29, 2013 by CNES, left, and on June 16, 2014 by DigitalGlobe, and annotated by Human Rights Watch, shows the Salahuddin palace in Tikrit, Iraq. (Human Rights Watch, CNES and DigitalGlobe/Associated Press)

Militants from the Islamic State group carried out a mass killing of hundreds of Iraqi soldiers captured when the extremists overran a military base north of Baghdad in June, an international watchdog said Wednesday.

The slaughter at Camp Speicher, which previously served as a U.S. facility, was one of the worst atrocities perpetrated by the Islamic State as it seized parts of northern and western Iraq.

According to Human Rights Watch, new evidence indicates that Islamic State fighters killed 560 to 770 men captured at Camp Speicher, a figure several times higher than initially reported.

Human Rights Watch said in late June that analysis of photos and satellite images showed that 160 to 190 men were killed in at least two locations between June 11 and 14.

Wednesday’s report said the revised figure was based on analysis of new satellite imagery, militants’ videos and a survivor’s account that confirmed the existence of three more “mass execution sites.”

This file image posted June 14 on a Web site used by militants appears to show fighters from the Islamic State leading captured Iraqi soldiers dressed in plain clothes after taking over a base in Tikrit, Iraq. (Associated Press)

After the incident, the soldiers were listed as missing, prompting their families to stage demonstrations in Baghdad to pressure authorities for word on their fate. On Tuesday, dozens of family members stormed parliament in Baghdad after scuffling with security guards. They forced the speaker to call a session to discuss the missing soldiers.

At the parliament session Wednesday, the soldiers’ families accused authorities of “selling our sons” by ordering many of the soldiers to abandon their posts and leave Camp Speicher in civilian clothes.

Once outside the base, hundreds were captured, said Mohammed al-Assi, a representative of the families.

Acting Defense Minister Saadoun al-Dulaimi denied that any orders had been issued for the abandonment of Camp Speicher.

Survivor Thaer Abdul-Karim told lawmakers that a military commander ordered the soldiers June 12 to hand over their weapons and leave the camp.

Abdul-Karim said the troops were told there were military trucks waiting for them at a nearby highway to take them to a base near Baghdad. Instead, he said, the soldiers, in civilian clothes, were seized by gunmen waiting for them on the highway.

The gunmen later started to shoot them, he said.

“We panicked after seeing our colleagues being shot dead,”
Abdul-Karim said. “There was a state of chaos, and some started to run away, and I managed to escape from the place.”