Rights groups said Wednesday that the executions by the Iraqi state of 36 men over a 2014 massacre claimed by the Islamic State group were failing to deliver justice and security.

Iraq on Sunday hanged 36 men found guilty of involvement in the killing of up to 1,700 military recruits who were captured by IS and allied militants from Camp Speicher, near the city of Tikrit.

The executions came after trials that rights watchdogs and the United Nations said failed to meet most basic standards.

"When such a high-profile trial as this is mired with due process violations, what faith can anyone, on any side, have in Iraq's justice system," asked Human Rights Watch in a statement.

HRW pointed out that among the 36 who were hanged were 24 men who had an earlier death sentence in the same case overturned over procedural errors.

The group of defendants was then expanded and death sentences handed down again in February 2016 after a one-day hearing.

Amnesty International also criticised the hangings.

"Executing men who were forced to 'confess' under torture and were not given a proper chance to defend themselves is not justice," the London-based group said.

"Relying on executions to counter Iraq's security challenges is completely misguided. It does not address the root causes of deadly attacks and will only serve to perpetuate the cycle of violence," it argued.

According to Amnesty, at least 81 executions have been carried out in Iraq so far this year and at least 123 people sentenced to death.

Sunday's hangings were attended by officials and relatives of Speicher victims.

The Speicher massacre is considered one of IS's worst crimes since it took over large parts of the country in 2014 and proclaimed its "caliphate".