mosul refugee
© Goran Tomasevic / ReutersA newly displaced woman carries her child at a check point in Qayyara, east of Mosul, Iraq October 26, 2016.
Terrorist group Islamic State has forced tens of thousands of people, mostly women and children, into Mosul from surrounding areas to serve as human shields, the UN human rights office has said. It comes as Shiite militias announced an imminent attack on the city.

Islamic State (IS, formerly ISIS/ISIL) is preparing for a major attack on its Iraqi stronghold by the Iraqi army and its allies, possibly including Shiite militias, Kurdish militias and Turkish forces, with the US-led coalition providing air support.

Ahead of the impending attack, the terrorists have taken steps to deter the offensive, including launching raids on communications channels, setting fire to oil and chemicals sites, and abducting people from areas around Mosul.

On Wednesday alone, hardline Sunni militants killed at least 232 people around Mosul, who were resisting relocation, UN human rights spokeswoman Ravina Shamdasani told a news briefing

"Many of them who refused to comply were shot on the spot," she said, citing reports corroborated by the UN that were "by no means comprehensive but indicative of violations."

Mosul is Iraq's second most populous city after the capital Baghdad. Located in a predominantly Sunni region in the north, it is estimated to have several million residents, even after IS purged non-Sunni minorities, killing them or forcing them to leave.

The offensive, first announced two weeks ago, is likely to take a heavy toll on the civilian population as the city will become an urban battleground. Humanitarian organizations called on the attacking forces to avoid targeting civilian infrastructure and to take care to minimize civilian casualties.

The offensive is not yet at full scale, as the different parties involved seem unable to overcome a number of differences. The Iraqi government objects to Turkey's presence on its soil, saying Turkish troops were not invited. Turkey does not want Shiite militias and Kurds to be part of the operation, saying they would be targeting Sunni and ethnic Turkoman civilians living in the region. Ankara also sees the Iraqi Kurds as allies of Turkish Kurdish insurgents.

As the stalling continues, the Shiite militias, collectively known as Hashid Shaabi, or Popular Mobilization Forces, announced on Friday that they are launching an offensive on Mosul in "a few days or hours."

Militia spokesman Ahmed al-Asadi said their forces would move in the direction of Tal Afar, a neighborhood about 55km west of Mosul. Turkey's foreign minister, Mevlut Cavusoglu, said on Wednesday that Turkish troops would "take measures" if the militias attack Tal Afar.