GENEVA: Islamic State forces in Iraq have abducted "tens of thousands" of men, women and children from areas around Mosul and are using them as human shields in the city as Iraqi government troops advance, the UN human rights office said on Friday.

The ultra-hardline Sunni militants killed at least 232 people on Wednesday, including 190 former Iraqi security forces (ISF) and 40 civilians who refused to obey their orders, 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".