The Iraqi Government on Sunday hanged 36 people convicted of involvement in the 2014 Camp Speicher massacre near Tikrit, in which at least 1,500 Iraqi Air Force cadets were killed.
The DAESH terrorist organisation claimed responsibility for the massacre.
"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 Agence France Presse.
"The governor of Dhiqar, Yahya al-Nasseri and Justice Minister Haidar al-Zamili were present to oversee the executions," Abdelhassan Dawood said.
"They were transferred to Nasiriyah last week after the president approved the executions," he said, referring to the necessary green light from Fuad Masum.
Iraq executed by hanging to 36 ISIS terrorists involved in the massacre of 1.700 iraqis in Tikrit pic.twitter.com/1hfw8aLFd3
— M-H (@TheIraqiArab) August 21, 2016
Following the deaths of more than 300 people in the worst ever single bomb attack to strike Baghdad last month, Prime Minister Haider al-Abadi had said he wanted to expedite the execution of inmates sentenced to death in terrorism cases.
Dhiqar's governor confirmed to AFP that the executions were carried out by hanging.
His spokesman said that around 400 of the Speicher massacre victims were from Dhiqar Province, which is predominantly Shia and located in Iraq's south.
"Tens of relatives attended the executions," said Dawood. "They shouted Allahu Akbar [God is greatest], they were happy to see those people dead."
Among them was Najla Shaab, a 30-year-old woman whose husband was killed in the massacre, leaving her to raise their children alone.
"Thank you God, it's a fair punishment for the worst crime, a triple crime of killing, throwing bodies in the river and burying people alive," she told AFP by phone.
One of the sites of the massacre was the former river police building inside former president Saddam Hussein's palace complex in Tikrit.
Human rights groups criticised the executions, saying basic legal standards were not met during the trails.
Amnesty International had slammed Iraq's systematic use of the death penalty following the 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.
The United Nations had criticised Abadi's call to speed up executions, which according to Amnesty already topped 100 for 2016 before Sunday's hangings.
"Fast-tracking executions will only accelerate injustice," UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said earlier this month.