Combined with a call by the country's top Shiite cleric Grand Ayatollah Ali al-Sistani, the massacre created outrage and helped mobilise Iraq's Shia militias in the fight against ISIS. Last year, militants released photos and videos documenting the massacre. Earlier this year, the bodies of the deceased were found in a mass grave.
"The executions of 36 convicted over the Speicher crime were carried out this morning in Nasiriyah prison," a spokesman for the governor's office in Dhiqar, the province of which Nasiriyah is the capital, told AFP while confirming that the executions were carried out by hanging.
Haider al-Abadi , Iraq Prime Minister, had said last month that he wanted to expedite the execution of inmates sentenced to death in terrorism cases. The timing of his comments corresponded closely with the worst ever single bomb attack in Baghdad that killed over 300 people.
His spokesman said that around 400 of the Speicher massacre victims were from the Dhiqar province, which is predominantly Shiite and located in Iraq's south.
"Tens of relatives attended the executions. They shouted Allahu Akbar (God is greatest), they were happy to see those people dead," Abdelhassan Dawood, a senior official believed to be the spokesman of Haider al-Abadi was quoted saying.
"The governor of Dhiqar, Yahya al-Nasseri and Justice Minister Haidar al-Zamili were present to oversee the execution. They were transferred to Nasiriyah last week after the president (Fuad Masum) approved the executions," he added.
Criticism for executions
Prominent organizations such as the United Nations and Amnesty International have criticized the executions carried out in Iraq.
Amnesty International for instance had raised concern over Iraq's execution of 22 other people in May this year.
"The use of the death penalty is deplorable in all circumstances, and it is particularly horrendous when applied after grossly unfair trials marred by allegations of confessions extracted under torture as is frequently the case in Iraq," the group's Iraq researcher Diana Eltahawy said in a report.
The United Nations had also criticised Abadi's call to speed up executions. Amnesty added that before Sunday's hangings, the number of executions had already topped 100 for 2016.
"Fast-tracking executions will only accelerate injustice," UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said earlier this month.