Baghdad (CNN) -- Iraqi authorities executed 21 people, including three women, after they were convicted of terrorism and spent months on death row, the nation's Ministry of Justice reported Tuesday.
The prisoners were put to death on Monday in what appears to be the latest of several executions carried out by authorities in recent months, despite a United Nations call for restraint.
Since November, nearly 90 people have been executed, according to the United Nations. Sixty-five of them were put to death in the first 40 days of 2012.
"Our main concern is what were these people actually convicted of?" said Joe Stork, deputy Middle East director at Human Rights Watch. "Terrorism does not tell us very much."
Stork also expressed concerns over the nation's judicial process.
Violence in Iraq escalates "What kind of trial did these people receive?" he asked. "We have unfortunately lots of experience to indicate that trials are very problematic, particularly security related trials in terms of providing defendants with the legal counsel."
Earlier this year, U.N. High Commissioner for Human Rights Navi Pillay said she was shocked at reports of mass executions. "Even if the most scrupulous fair trial standards were observed, this would be a terrifying number of executions to take place in a single day," Pillay said then.
"Most disturbingly, we do not have a single report of anyone on death row being pardoned, despite the fact there are well documented cases of confessions being extracted under duress," Pillay said.
The ministry also announced that it released 625 inmates on Monday from detention facilities across Iraq, indicating that the prisoners had completed their sentences.
Meanwhile on Tuesday, six Iraqi security force members were killed by gunmen in two shootings that targeted checkpoints.
In the al-Wazirya neighborhood of northeastern Baghdad, gunmen shot dead two Iraqi soldiers, authorities said.
Gunmen also attacked an army checkpoint in al-Mashahda, an area north of Baghdad, with small arms fire. Four Iraqi soldiers were killed.
Wave of violence in Iraq claims more than 80 lives