Islamic State fighters forced thousands of civilians to retreat with them from Hamam al-Alil as Iraqi police were recapturing the town, and moved them towards Mosul airport, the UN said Tuesday.
Iraqi forces retook the key town from the jihadists on Monday, in a major win in its offensive to wrest back the nearby city of Mosul.
But the IS fighters did not leave the town alone: UN rights office spokeswoman Ravina Shamdasani told reporters in Geneva the agency had received reports that the jihadists "forcibly moved about 1,500 families from Hamam al-Alil town to Mosul airport" on November 4.
The UN has for weeks warned that IS was forcing civilians living in districts around Mosul into Iraq's second city, hoping to use them as human shields in an upcoming battle.
Shamdasani also said the rights office had received information that the jihadists had "abducted at least 295 former Iraqi Security Forces personnel" from areas around Mosul.
"Between November 1-4, 195 former ISF personnel were reportedly abducted in several villages in Tel Afar, and at around midnight on November 3, at least 100 former ISF officers were abducted from Mawaly Village, about 20 kilometres west of Mosul," she said.
"The fate of all of these civilians is unknown for the moment," she said.
When the Iraqi forces recaptured Hamam al-Alil, they said they found a mass grave at an agricultural college, with the offensive's Joint Operations Command saying "100 bodies of citizens with their heads cut off" had been uncovered.
The UN could not immediately confirm the information, and Shamdasani said her office was still looking into reports last month that IS had killed 50 former Iraqi police officers at the same location.
Iraqi forces have been tightening the noose around Mosul since launching the offensive on October 17, with elite troops last week breaching city limits.
Upping pressure on the jihadists, the Kurdish-Arab Syrian Democratic Forces (SDF) alliance on Saturday launched its own offensive on IS's other main bastion, the Syrian city of Raqa.
Raqa and Mosul are the last major cities in Syria and Iraq under the jihadists' control and their capture would deal a knockout blow to the self-styled "caliphate" IS declared in mid-2014.