"Islamic State" (IS) fighters have captured thousands of Iraqi villagers fleeing their homes in northern Iraq, according to the United Nations and human rights advocates.

The UN High Commission for Refugees (UNHCR) said IS militants captured 3,000 Iraqis

"UNHCR has received reports that ISIL captured on 4 August up to 3,000 IDPs (internally displaced people) from villages in Hawiga District in Kirkuk Governorate trying to flee to Kirkuk city. Reportedly, 12 of the IDPs have been killed in captivity," the UNHCR report said.

The UNHCR claim followed on a report by the Iraqi Observatory for Human Rights, a non-governmental organization, that said about 1,900 villagers had been captured. The Observatory said as many as 120 IS militants were using people as human shields against attack from Iraqi Security Forces.

The militants have also executed tens of villagers, including six who were burnt to death.

The IS has a large swathe of territory straddling the Iraq/Syrian border, which it first seized in 2014. But a US-led coalition has launched a sustained air campaign against the militants. Some 3.4 million Iraqis have been displaced by the relentless fighting.

Battle for IS strongholds

Even though the US and its allies have made territorial gains over the past year the jihadists still maintain their de facto capitals - Mosul in Iraq and Raqqa in Syria.

In July, the UN asked the global community for $284 million to prepare aid for an assault on Mosul, as well as $1.8 billion to deal with the aftermath.

So far, the request has gone unanswered receiving virtually no response, according to the UN Financial Tracking Service.

Nonetheless, the UNHCR has begun building IDP shelters on the outskirts of Mosul. One would house 6,000 displaced villagers and the other 15,000. That is a mere fraction of those expected to need shelter.

bik/rc (Reuters, AP)