Iraq has hanged 36 men convicted of killing up to 1,700 military recruits at a former US base in 2014.
The massacre at Camp Speicher, near Tikrit, was carried out by fighters from self-styled Islamic State terrorist group as it seized territory across northern Iraq.
Outrage over the massacre of the mostly Shia cadets helped mobilize Iraqi militias in the fight against IS. IS militants released photos and video documenting the massacre in 2014. Mass graves were found a year later, BBC reported.
The graves were discovered when Iraqi government forces recaptured the area.
"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.
The spokesman said Justice Minister Haidar al-Zamili was present at the executions.
Prime Minister Haider al-Abadi had said after last month's Baghdad bomb blast that killed more than 300 people that he wanted to speed up executions of terrorism convicts.
Those executed on Sunday, all believed to be Iraqi citizens, had been sentenced to death in February.
Photos and videos published by IS after the massacre showed soldiers being loaded on to vehicles and forced to lie face down on the ground before being shot dead.
