Iraqi protesters threatened to intensify their demonstrations and bring about "chaos" as the death toll approached 500 and scores were still missing.
For almost three months, the country has been rocked by anti-government protests, with the political elite accused of corruption and failing to provide public services and employment.
The semi-official Human Rights Commission confirmed that 490 protesters had been killed in the uprising, including 33 activists who were assassinated.
"The death toll includes 15 members of the security forces," Ali Al Bayati, a member of the commission, told The National.
"The total number of abductions have amounted to 68. Twelve of them have been released and the fate of the others remains unknown."
The commission pushed the government to form a committee within the Interior Ministry to investigate the increase in the number of protesters abducted and secure their release.
About 2,800 people have been arrested since October. Most have been released but about 100 remain in detention centres.
“There are ongoing investigations into the remaining 100 protesters," Mr Al Bayati said. "There is some evidence that shows their involvement in the devastation but the commission is attempting to release them all.”
The body has not openly blamed any group for the violence.
The UN said it had received credible allegations of deliberate killings, abductions and arbitrary detentions by armed men described as militia, "unknown third parties" and "armed entities".
Iraq's political crisis is now as serious as any other since the overthrow of former dictator Saddam Hussein 16 years ago, and its leaders seem ill-equipped to deal with it.
Many Iraqis languish in poverty without jobs, health care or education and the government has done little to address the demands of protesters.
Prime Minister Adel Abdul Mahdi resigned last month but will remain in the position until his successor is named. However, Parliament has yet to find a replacement.
Protesters want a candidate with no party affiliation, to take over from Mr Abdul Mahdi.
"We reject any candidate that came into political power after 2003, even if the person is not tied to the ruling parties," a committee formed by demonstrators said.
The committee said protesters declined to nominate a candidate due to the "high level of corruption in Parliament and their links to Iran".
"Our revolution will continue until we win back our country."
On Thursday, President Barham Salih refused to designate the nominee of an Iran-backed parliamentary bloc, Assad Al Eidani.
Mr Salih said he would rather resign than appoint someone to the position who would be rejected by protesters.
His decision was met with criticism by Iran-backed politicians in Baghdad.
The Hezbollah Brigades, or Kataib Hezbollah, called Mr Salih's move “suspicious”.
“We know that he is carrying out an American will that aims to pull the country towards chaos,” the group said.
It said the president had breached the constitution “by refusing to carry out his duties” to name the candidate chosen by Parliament’s largest bloc.
Mr Salih on Sunday stressed the need to "respect the will of the people to implement reforms and reject any external interference in domestic politics".