BAGHDAD (AP) — Iraq on Sunday executed 36 men convicted of taking part in the Islamic State group’s massacre of hundreds of soldiers in 2014, officials said.

The men were hanged at the Nasiriyah prison in southern Iraq, according to provincial Gov. Yahya al-Nasiri. A Justice Ministry official, who spoke on condition of anonymity because he was not authorized to brief reporters, confirmed the executions.

IS captured an estimated 1,700 soldiers after seizing Saddam Hussein’s hometown of Tikrit in 2014. The soldiers were trying to flee from nearby Camp Speicher, a former US base just outside the northern city. Shortly after taking Tikrit, IS posted graphic images of gunmen shooting the men dead after forcing them to lie face-down in a shallow ditch.

The Speicher massacre sparked outrage across Iraq and partially fueled the mobilization of Shiite militias in the fight against IS, a Sunni extremist group. The militias now rival the power of Iraq’s conventional armed forces.

Iraqi forces arrested dozens of men allegedly linked to the massacre after retaking Tikrit in 2015 with the help of US-led airstrikes. The men executed on Sunday were sentenced to death by an Iraqi court earlier this year.

The head of the provincial council in Salahuddin province, of which Tikrit is the capital, criticized the judicial process, saying some of the men executed Sunday had been tortured to extract confessions.

Some of them “were not even present at the scene of the crime,” Ahmed al-Karim told The Associated Press. “We support the death penalty for those who committed crimes,” but “the use of violence and torture (in Iraqi prisons) should be investigated.”

Prime Minister Haider al-Abadi has attempted to fast-track the implementation of death sentences following a series of large-scale bombings in and around Baghdad in recent months.

The United Nations criticized that policy earlier this month, saying that “given the weakness of the Iraqi justice system,” the rushed sentences risk causing “greater injustice.”

Iraq ranks among the top five countries in the world in the use of capital punishment, according to figures compiled by the rights group Amnesty International.