Kurdish fighters from Iraq, Syria and Turkey joined forces in northern Iraq Wednesday in a bid to reclaim areas lost to jihadists and rescue tens of thousands of civilians stranded without food or water in nearby mountains.

The fate of the civilians, many of them from the Yazidi minority who fled to the Sinjar mountains after an attack by the Islamic State (IS) group at the weekend, has sparked international concern.

In a series of raids west and north of their main Iraqi hub of Mosul in recent days, IS fighters took over the towns of Sinjar and Zumar, further secured the border with Syria by seizing Rabia, and they bagged several oilfields in the process.

A senior official from Iraq’s Patriotic Union of Kurdistan (PUK) party said Kurdish fighting units from the homegrown peshmerga, the Syrian-based PYD and the Turkish PKK had agreed to share responsibility for the ongoing counter-offensive.

“The fighters of West Kurdistan and the PKK are responsible for confronting Daash (IS’s former Arabic acronym) in Rabia and the Sinjar area,” said Hallo Penjweny, the PUK’s top official for the Mosul region.

“On our side, we are taking care of Zumar and the rest of the area north and east of Mosul,” he told reporters.

Sinjar is west of Mosul, Iraq’s second city.

West Kurdistan refers to the Syrian Democratic Union Party (PYD), which claims it has already retaken Rabia, but it remains unclear how much progress they have made in the Sinjar area.

Another PUK official warned it could be some time before the civilians can be rescued.

“The PKK is working to open a safe passage for the displaced; it is not easy and it will require days,” Harem Kamal Agha told AFP.

The UN Security Council warned Tuesday that the Islamic State may be held accountable for crimes against humanity for its systematic persecution of minorities in Iraq.

The council condemned IS and associated armed groups “in the strongest terms” for attacking and killing minorities, including Christians, as well as Iraqis who oppose their “extremist ideology.”

IS issued an ultimatum to tens of thousands of people from the Yazidi community on Saturday to convert to Islam, pay a religious fine, flee their homes or face death. Yazidis follow an ancient religion with links to Zoroastrianism. At least 40 children from those displaced from Sinjar were killed in the violence, UNICEF said Tuesday.

The Security Council said many Iraqis from Tal Afar and Sinjar have been forced to flee and seek refuge “while many others have been executed or kidnapped.”

Council members noted that “widespread or systematic attacks directed against any civilian populations because of their ethnic background, religion or belief may constitute a crime against humanity, for which those responsible must be held accountable.”

They stressed that all parties, including the Islamic State group, “must abide by international humanitarian law, including the obligation to protect the civilian population.”

“The biggest problem now is that they have no food. They have started hunting small animals in the mountains and they eat anything they can find,” he said. Abu Abbas, a 50-year-old Irrigation Ministry employee who fled Sinjar to Kurdistan, told AFP about the plight of his children and other relatives trapped in the barren Sinjar range.

An Iraqi Yazidi woman who fled the violence in the northern Iraqi town of Sinjar, cries as she stands among others at a school where they are taking shelter in the Kurdish city of Dohuk in Iraq's autonomous Kurdistan region, on August 5, 2014. (photo credit: AFP/SAFIN HAMED)

An Iraqi Yazidi woman who fled the violence in the northern Iraqi town of Sinjar, cries as she stands among others at a school where they are taking shelter in the Kurdish city of Dohuk in Iraq’s autonomous Kurdistan region, on August 5, 2014. (photo credit: AFP/SAFIN HAMED)

“Several children have died already and been buried in the mountain. All the women are giving their milk to the children, regardless of whether they are Yazidi, Muslim or Christian.”

“The elders who know some old natural springs are searching the mountain but it’s dangerous. On the other side, Daash is waiting for them. I think it will be difficult for any of them to survive longer than two or three more days,” he said.

Abu Abbas said he had received scant information on Wednesday because his relatives’ phone batteries had run out.

Iraqi government officials said 77 tonnes of food and water had been air-dropped since Tuesday.

The peshmerga are considered the most able military force in Iraq, but their regional government has been cash-strapped and they have struggled to hold the territory they grabbed when federal soldiers retreated in the face of an initial IS onslaught two months ago.

Their withdrawal from Sinjar, after hours battling IS militants, left civilians running for their lives.

Notable among them are the Yazidis, who are stigmatised as “devil-worshippers” by the jihadists because of their unique blend of beliefs and practices.

A Yazidi lawmaker broke down in tears during a parliamentary session Tuesday as she urged the government and the international community to save her people from being massacred or starved into extinction.

“We are being slaughtered; our entire religion is being wiped off the face of the earth. I am begging you, in the name of humanity,” said Vian Dakhil.