In a twist in the war inside Iraq, Kurdish officials have warned of the influx of Shia militias near Kirkuk, the oil-rich city in northern Iraq that has long been disputed between Kurdish, Arab, and Turkmen factions.

Both the Kurds and the Shia militias, allied with the Iraqi Government, have been trying to push back the offensive of the Islamic State. However, the arrival of thousands of Shia militiamen have prompted the Kurdish warnings of a new conflict.

Kurdish peshmerga moved into Kirkuk in June to secure the city against the Islamic State’s advance. Kurdish forces have subsequently fought the jihadists throughout Kirkuk Province, as the Shia militias and Iraqi forces challenged the Islamic State in other areas of Iraq.

An unnamed source told the Kurdish outlet Rudaw that a total of 8,000 Shia militiamen have been deployed in four military training bases. He said the armed groups include Khorasan, Iraqi Hezbollah, the Badr Brigade, and Asa’ib Ahl al-Haq.

The source asserted that a paramilitary force of 550 Shiite fighters is already inside Kirkuk city.

Najat Hussein, the head in Kirkuk of the largely-Shia Islamic Supreme Council of Iraq, said the militiamen were celebrating victory against the Islamic State alongside Kurdish peshmerga forces.

Sunni Arabs in the Kirkuk Provincial Council have opposed any participation of Shia militias in operations to liberate their towns and villages around Kirkuk, calling instead for local paramilitary forces.