The report of UN High Commissioner for Human Rights Louise Arbour said that the true number of fatalities from events in Andijan between 12-14 May was much higher.
"In the view of those interviewed, the actions of the armed and security forces were taken less with the intent of establishing law and order and re-arresting the prisoners that had escaped from the Andijan prison than with the aim of killing as many people as possible, including women and children."
Arbour's report added that the true toll could only be known for sure if there were an international commission of inquiry.
Uzbekistan's government has so far rejected any kind of international probe, and says its troops opened fire on terrorists and puts the death toll at 176.
But four UN investigators, who carried out over two weeks of interviews with witnesses in June, report that "consistent, credible eyewitness testimony strongly suggests that grave human rights violations, mostly of the right to life ... were committed by Uzbek military and security forces".
Uzbek refugees who fled to
Kyrgyz have been sent back
Interviews were also conducted with dozens of Uzbek survivors who successfully fled across the border into Kyrgyzstan. Their 24-page report added that: "It is not excluded - judging from the accounts of the eyewitnesses interviewed - that the incidents amounted to a mass killing".
Witnesses said at the time that more than 500 people were killed by troops putting down a popular protest against the trial of 23 local businessmen and the government of President Islam Karimov.
During the 13 May demonstration, the local prison was overrun, inmates freed and the regional administration building seized during the night. That afternoon there were "repeated shootings by security forces", leading to hostage-taking by the protesters, the UN report said.
The hostages, some of whom were taken to the occupied administration building, were later placed in front of the crowd as protection.
But soldiers and snipers began shooting indiscriminately, the report said, with witnesses estimating that "the number of killed during this most intensive shooting varied between 200 and 700".
Uzbek official response
Rejecting the need for an international investigation, Uzbek officials say they have already set up an independent commission to detail what happened.
"The attempts to depict the armed criminals as fighters for democracy once again demonstrate the proclivity of certain individual [UN] States to employ double standards in interpreting anti-terrorist efforts"
Uzbek permanent representative
at the UN
Official Uzbek political affairs spokesman Avazbek Khodjimetov told Aljazeera.net that the investigation was "being conducted within the framework of criminal legislation by the agencies of the General Prosecutor's Office of the Republic" and that governments and officials should wait for its conclusions before commenting.
In May, Uzbekistan's permanent representative at the UN, Alisher Vohidov told journalists that "the incorrect and arbitrary interpretation of the tragic events in Andijan" were perplexing.
"The attempts to depict the armed criminals as fighters for democracy once again demonstrate the proclivity of certain individual [UN] States to employ double standards in interpreting anti-terrorist efforts", he said.