More than a hundred prisoners are believed to be on death row in Iraq
The United Nations human rights office has urged Iraq not to use the death penalty, saying that fair trials cannot be guaranteed in the country's courts.
The call comes after 12 people were hanged on Sunday. There had been no executions in the previous 18 months.
The UN said there are particular concerns that evidence gathered by means of torture is being used, and many more executions may be pending.
The Iraqi government has not yet commented on the UN report.
"It is a matter of regret that, after a year and a half of non-application of the death penalty, executions have resumed", the UN High Commissioner for Human Rights and the UN mission in Baghdad said in a joint statement.
The UN Human Rights Office believes that another 115 prisoners may face execution in the near future.
"It is of particular concern that the prohibition of the use of evidence - including confessions - gathered under duress or torture is often violated in Iraq," the UN statement added.
An execution carried out after such a trial would, the UN says, constitute a violation of the right to life.
The BBC's Imogen Foulkes in Geneva says the UN's Human Rights Office would like to see capital punishment abolished worldwide.
But, in the immediate future, it is calling on Iraq to stop the death penalty until its judicial system is reformed.