IS kills hundreds of prisoners in Mosul as offensive closes in: UN

Islamic State (IS) 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 militants killed at least 232 people on Wednesday, including 190 former Iraqi security forces 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".

"These reports have been corroborated to the extent possible," she added, stressing that the number of people killed in recent days may be even higher. 

Those being executed have included civilians who have refused to comply with the relocation orders and those who previously worked for the government security services.

Shamdasani said the execution-style killings come as IS pushes forward with its strategy of forcing people living near the northern Iraqi city into the heart of Mosul, the group's last bastion in Iraq.  

The rights office has said the militants aim to use these people as "human shields" in the ensuing battle against US-backed elite Iraqi troops. 

"ISIL has been forcing tens of thousands of people from their homes in some districts around Mosul," Shamdasani said.

At least 16,500 people have been displaced since 17 October, the International Organisation for Migration said on Friday - over half of them are still within Mosul district.

As militants inside the city prepare for the looming street battles, Iraqi forces announced one of their biggest ever finds in territory seized back from IS - a three-kilometre long tunnel and a huge bomb-making lab.

"Iraqi anti-terrorism forces uncovered the longest IS tunnel [so far found] - it is three kilometres long and stretches from Janin military base to the east of Mosul to the centre of Nineveh," a security source told Iraqi news site al-Sumaria.

Iran-backed offensive opening

Also on Friday, Iranian-backed Iraqi paramilitary groups announced they are to launch an offensive against IS positions west of Mosul, assisting in the military campaign to take back the city, a spokesperson said.

The operation will target an area close to Turkey and where a sizeable ethnic Turkmen population lives, likely causing alarm in Ankara.

The militias, collectively known as al-Hashd al-Shaabi or Popular Mobilisation Units (PMUs), have completed preparations to move in the direction of Tal Afar, a stronghold of IS west of Mosul, from their positions in Qayyara just south of the city.

"A few days or hours separate us from the launch of operations there," spokesman Ahmed al-Asadi told state TV.

The population of Tal Afar, about 55km west of Mosul, was a mix of Sunni and Shia ethnic Turkmen until Shia fled the town after IS militants took over the region in 2014, declaring a caliphate over parts of Iraq and neighbouring Syria.

Turkey's Foreign Minister Mevlut Cavusoglu said on Wednesday his country, which has troops deployed north of Mosul inside Iraqi territory, will take measures if there is an attack on Tal Afar.

Turkey fears the use of Shia militias in the US-backed offensive on Mosul will lead to sectarian strife in the mainly Sunni region, and cause an exodus of refugees.

Earlier announcements by the PMUs that they will be involved in the offensive on Mosul, IS's last major stronghold in Iraq, triggered warnings from human rights groups of sectarian violence in the mainly Sunni province.

The PMU officially reports to the Shia-led government of Prime Minister Haider al-Abadi, who announced the start of the offensive on Iraq's second largest city on 17 October, with the backing of a US-led coalition.

The PMU was formed in 2014 to help push back IS's sweeping advance through the northern and western provinces.

Amnesty International said that in previous campaigns, the Shia militias have committed "serious human rights violations, including war crimes'' against civilians fleeing Islamic State-held territory.

The UN in July said it had a list of more than 640 Sunni Muslim men and boys reportedly abducted by a Shia militia group in Fallujah, a former militant stronghold west of Baghdad, and about 50 others who were summarily executed or tortured to death.

The government and the PMUs say a limited number of violations had occurred and were investigated, but they deny abuses were widespread and systematic.

Kurdish independence

Amid Kurdish efforts to recapture Mosul, Iraq's Kurdish autonomous region plans to renew its push for independence once the city is retaken, its prime minister said on Friday.

"The time has long been ripe for it, but we are currently concentrating on the fight against IS," Kurdish regional prime minister Nechirvan Barzani told Germany's Bild daily.

"As soon as Mosul is liberated, we will meet with our partners in Baghdad and talk about our independence," he said according to a translation from the German.

The premier of the Kurdistan Regional Government added that "we have been waiting for too long; we thought that after 2003 there would be a real new beginning for a democratic Iraq. But this Iraq has failed. 

"We are not Arabs, we are our own Kurdish nation ... At some point there will be a referendum on the independence of Kurdistan, and then we will let the people decide."

In February, Kurdish President Massoud Barzani, the premier's uncle, had called for a referendum on a Kurdish state in northern Iraq, raising tension with Baghdad, which opposes secession.

The Kurdish Peshmerga have fought with Iraqi government forces in the offensive to retake Mosul from IS.

Barzani said he estimates the coalition would need three months to retake the city and asked for more German weapons to aid his forces, as well as EU aid for refugees from the conflict.

On the battle against IS, he said "we have taken the outlying districts quickly, but it's not clear how strongly IS will defend the city itself.

"We are seeing that they have hundreds of suicide bombers, they must have entire factories where they are making the explosives. That is the greatest threat to the offensive."