At least 1,075 people, most of them civilians, have so far been killed in strife-torn Iraq during June, according to UN monitors.
UN spokesperson Rupert Colville said the figure "should be viewed very much as a minimum".
The UN human rights team in Iraq reports at least 757 civilians died in Nineveh, Diyala and Salahuddin provinces between June 5 and 22, BBC reported Tuesday.
At least another 318 people were killed during the same time in Baghdad and areas in southern Iraq.
Colville added that it included some verified summary executions and extra-judicial killings of civilians, police officers and soldiers who had stopped fighting.
This month has witnessed insurgents, spearheaded by Islamists fighting under the banner of the Islamic State of Iraq and Greater Syria (ISIS), overrunning a swathe of territory in the north and west including the second-biggest city, Mosul.
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In its report on Iraqi deaths in June, the UN cites the example of 15 Shia civilians who were abducted from a village in Salahuddin province and killed. It also reports that a further 45 unidentified bodies were found on Tigris river's banks.
In addition, UN human rights officers in Iraq have confirmed reports of summary executions, in which a person is accused of a crime and then immediately killed without benefit of a full and fair trial, carried out by Iraqi security forces as they withdrew from the Nineveh Operations Command headquarter in Mosul city, as it was overrun by ISIS fighters.