Decision follows prime minister's recent vow to expedite execution of convicts sentenced to death in terrorism cases.
Iraq has hanged 36 men convicted over the 2014 massacre of hundreds of military recruits, government officials say.
They had been found guilty of involvement in the "Speicher" massacre, named after a base near Tikrit where up to 1,700 recruits were kidnapped before being executed in a massacre claimed by the Islamic State of Iraq and the Levant (ISIL) group.
"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 governor of Dhiqar, Yahya al-Nasseri, and Justice Minister Haidar al-Zamili were present to oversee the executions," Abdelhassan Dawood said.
READ MORE: Escaping an Islamic State execution in Iraq
"They were transferred to Nasiriyah last week after the president approved the executions."
Dawood was referring to the necessary green light from Iraqi President Fuad Masum.
Following the death of more than 300 people in the worst ever single bomb attack to strike Baghdad last month, Haider al-Abadi, Iraqi prime minister, had said he wanted to expedite the execution of inmates sentenced to death in terrorism cases.
Nasseri confirmed to AFP news agency that the executions were carried out by hanging.
His spokesman said that about 400 of the Speicher massacre victims were from Dhiqar, which is predominantly Shia and located in Iraq's south.