Jose Diaz, a spokesman for the High Commissioner, today said that the crackdown amounted to "mass killing."
The crackdown in Andijon came after large-scale protests over a court ruling that jailed some 20 people for alleged Islamic extremism.
The Uzbek government says that during the protests, an armed group of Islamic militants raided the jail, freeing prisoners and killing hostages. Government troops were then called in to crush the uprising.
The government says 187 people were killed. The government also says that half of the killed were militants.
Human rights advocates say up to 750 people were killed in the crackdown.
The UN's new report says that only an international inquiry can reveal all the facts of what happened in Andijon.
Uzbekistan has so far refused such an inquiry, allowing only international monitoring of its own probe.