UN Human Rights spokesman Rupert Colville cited a report of 17 civilians killed in just one street on Wednesday, ABC News reported on Friday.

"The full extent of civilian casualties is not yet known, but reports received by ... the UN Mission in Iraq suggest that the number of people killed may run into the hundreds and the number of wounded is said to be approaching one thousand," Colville said.

Four women had killed themselves after being raped, 16 Georgians had been kidnapped, and prisoners released by the militants had been looking to exact revenge on those responsible for their incarceration, he said.

Navi Pillay, the top United Nations human rights official, also said that she was "extremely alarmed" by reports of "summary executions and extrajudicial killings" in Mosul.

The terrorist group is composed of Takfiri extremists. Most of Iraq's armed forces fled before ISIL's approach. Human Rights Watch has documented a pattern of summary executions and torture in other areas of Syria and Iraq that it has conquered.

Reports from Syria over the past year document that ISIL often beheads those it executes.

"The possibility that ISIS [ISIL] will repeat the atrocities it has committed in other parts of Iraq, and impose the same intolerant and abusive rule as it has in Syria, is deeply troubling," said Nadim Houry, deputy Middle East director at Human Rights Watch.

The ISIL has been posting pictures and videos of their assault in Mosul, Tikrit and Kirkuk, some of them showing bodies of Iraqi soldiers cut into pieces.

Local Iraqi newspapers say tens of people have been executed by ISIL, including Shia Muslims, Christians and other followers of other religious sects that do not abide by the Takfiri intolerance.

NTJ/MB