Iraqi forces stormed an ISIL camp and retook several villages from the extremists on Wednesday, as Baghdad launched operations to rid a northeastern desert region of insurgents.
The offensive — which comes just two months after Iraq declared victory over ISIL — is also targeting members of the little-known "White Flag" militant group, which is believed to have Kurdish links.
"With the goal of enforcing security and stability, destroying sleeper cells, and continuing clearing operations, an operation was launched in the early hours of Wednesday morning to search and clear areas east of Tuz Khurmato (50 kilometres from Kirkuk city)," the Iraqi armed forces said.
The action also aims to secure bridges, roads and junctions between Baghdad and Kirkuk, the statement added.
Baghdad wants to consolidate its control of a mountainous area near the Iranian border through which it plans to transport crude from the oil-rich city of Kirkuk to Iran's Kermanshah refinery by truck.
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The transportation of oil — which was announced by Baghdad in December — was scheduled to start last week but oil officials failed to give reasons for the delay other than that they were technical in nature.
Wednesday's operations were carried out by the Iraqi army's 9th armoured division, the interior ministry's elite Emergency Response Division and fighters from the Hashed Al Shaabi, an Iran-backed umbrella group of mainly Shiite militias also known as the Popular Mobilisation Units (PMUs).
The soldiers and militiamen are targeting remaining ISIL militants, as well as fighters from the so-called "White Flag" insurgent group, which in recent months has been accused of conducting terrorist activities and targeting lawmakers in northeastern Iraq. In December last year, members of Kirkuk's provincial council also accused the group of kidnapping 11 civilians and raiding homes in Tuz Khurmatu.
Military officials have acknowledged the existence of White Flag but refused to comment on its composition or leadership.
The group's ideology — if any — and ambitions are unclear but it is believed to have been established at the end of last year by Kurdish fighters displaced from areas between Kirkuk and Tuz Khurmatu, according to Hisham Al Hashimi, a security analyst in Baghdad. It came after pro-government forces retook Kurdish-held areas contested by both Erbil and Baghdad in October last year.
The PMUs believe the White Flag has between 200 and 500 fighters while other security officials claim the insurgents number somewhere between 500 and 1,000.
Baghdad declared victory over ISIL in December, after taking back all of the territory captured by the militants in 2014 and 2015.
UN experts this week voiced their concerns, however, that ISIL continues to pose "a significant and evolving threat around the world" despite its recent setbacks in Iraq and Syria.
In a report presented to the Security Council on Tuesday, the experts said ISIL "has lost its focus on conquering and holding territory" but is continuing "to give prominence to external attacks".
The fight against ISIL militants is entering a new phase with more focus on "less visible networks of individuals and cells acting with a degree of autonomy", the report said.
It came as Iraqi prime minister Haider Al Abadi confirmed on Tuesday a planned reduction in the number of US-led anti-ISIL coalition forces in the country but stressed the ongoing need for air support.
"Talks have been going on for the past year to gradually reduce the number of the (coalition) forces" from the current figure of roughly 10,000, Mr Al Abadi said.
The coalition provided pivotal support to Iraqi forces in their fight against ISIL, especially in the battle to dislodge the group from Mosul — its de facto capital in northern Iraq — in July.
Mr Al Abadi also said the threat from ISIL was not over.
"There is still a danger inside Syrian territory. We control the borders, but there could be a real danger," he said.
"We need significant air cover to monitor the desert and terrorist movements. We need efforts from the coalition and … want to do a fully successful job."