Iraqi authorities executed at least 65 people in the first 40 days of 2012 for various offenses, including 14 on a single day, Human Rights Watch said Thursday.
Joe Stork, deputy Middle East director of the New York-based advocacy group, said that Iraqi authorities appear to have given the "green light to execute at will."
The group said trials often violate international standards. Many defendants are unable to challenge the evidence against them, which may include coerced confession.
HRW said that a justice official informed them 14 people were put to death on Wednesday alone, and that more executions should be expected.
"The government needs to declare an immediate moratorium on all executions and begin an overhaul of its flawed criminal justice system," said Stork.
The report said Iraq authorizes the death penalty for close to 50 crimes including terrorism, kidnapping, and murder, but also for offenses like damage to public property.
Telephone calls to Iraqi justice ministry officials to comment on the report were unanswered.
Iraq primarily uses hanging as a method of execution.
Meanwhile, thousands of followers of an anti-American cleric rallied Thursday in Baghdad to celebrate the December withdrawal of U.S. forces from the country.
The celebration took place in the main square of the Shiite neighborhood of Sadr City, the political stronghold of cleric Muqtada al-Sadr.
Men and boys waved Iraqi flags and raised banners praising those who fought against the U.S. presence in Iraq. Women were mostly absent.
"Our congratulations to the Iraqi people for the departure of the occupiers and the liberation of Iraq," one banner read.
Al-Sadr, who is currently in Iran where his movement says he is completing his religious studies, addressed his supporters by video link and urged the Iraqi government to release all the Sadrist detainees kept in Iraqi prisons.
"The next phase in Iraq should be the phase of construction and building in order to ensure a prosperous future for our country," said al-Sadr.
The U.S. completed its military withdrawal from Iraq in December 2011, but Sadrist lawmaker Jawad al-Shuhaili said the movement postponed celebrating it until the end of the Arbaeen, a 40-day period of mourning following the anniversary of the death of Imam Hussein, a revered Shiite figure.