• Iraqi forces entered the city of Kirkuk in Iraqi on Monday, capturing key government buildings including the Kirkuk governor's building.
• The incursion into the Kurdish-controlled area prompted thousands of Kurdish residents to flee, with international aid groups warning of the humanitarian fallout.
• Amid escalating tensions, Germany's defense ministry withdrew 140 military trainers stationed in northern Iraq to instruct peshmerga fighters involved in the fight against the "Islamic State."

Iraq's elite counter-terrorism forces on Monday entered Kirkuk and captured key government buildings in the Kurdish-controlled city, according to security sources. They raised the Iraqi flag over the provincial council's headquarters in Kirkuk and took control of the governor's building.

Read more: Kirkuk: What you need to know about the Kurdish-Iraqi dispute

Turkey has offered to help Iraq's federal government oust Kurdish fighters from Kirkuk after reports that fighters of Turkey's outlawed Kurdistan Workers' Party (PKK) were inside the oil-rich city.

Tensions between Baghdad and Iraqi Kurdistan have escalated since the the Iraqi Kurds overwhelmingly voted last month for an independent state in a non-binding referendum, which controversially included disputed territories such as Kirkuk.

What you need to know

• Following a controversial Kurdish independence referendum, Iraqi forces gave Kurdish forces a Sunday deadline to retreat to positions agreed upon in a 2014 accord.
• When Kurdish forces failed to do so, Iraqi security forces advanced on areas surrounding oil-rich Kirkuk, culminating in the capture of oil fields, regional government buildings, an airport and a military base on Monday.
• Kurdish peshmerga forces retreated, effectively allowing Iraqi security forces and Iranian-backed Shiite militias to move into the city unopposed.

'Impose security'

Iraqi state TV reported that Iraqi forces had taken control of "vast areas" outside of Kirkuk city. 

Kurdish peshmerga forces reportedly retreated back from positions outside the city, but were setting up defenses in the city as thousands of civilians fled in cars north to Erbil and Sulaymaniyah. The move by Iraqi forces prompted the German military to withdraw 140 military trainers deployed in northern Iraq to instruct peshmerga fighters.

Read more: What is the Iraqi Kurdish independence referendum?

Prime Minister Haider al-Abadi ordered security forces "to impose security in Kirkuk in cooperation with the population of the city and the peshmerga." He said that instructions were given for forces to stay out of the city.

The Kurdistan Region Security Council claimed peshmerga had destroyed several US-supplied Humvees belonging to the PMU. Hemin Hawrami, an adviser to Kurdish President Masoud Barzani, quoted the peshmerga command as saying Abadi's government would "pay a heavy price" for the assult on Kirkuk.

US: 'Avoid additional escalatory actions'

The US Defense Department, which has supplied and trained both the peshmerga and Iraqi army, urged its two allies in the war against the "Islamic State" (IS) "to avoid additional escalatory actions." It added that it opposed destabilising actions that distract from the battle against IS militants.

Later, US President Donald Trump said the US will not take sides, but expressed disappointment at the escalating dispute between two allies.

Read more: The Middle East's complex Kurdish landscape

"We don't like the fact that they're clashing. We're not taking sides," Trump told reporters. "We've had for many years a very good relationship with the Kurds as you know and we've also been on the side of Iraq, even though we should have never been there in the first place."

The Iraqi troops and the Kurdish peshmerga fighters have been engaged in a standoff since Saturday, when they took positions on opposite banks of a river on the southern outskirts of the city of Kirkuk. 

Kurdish forces were given a deadline of 2 a.m. local time Sunday (2300 UTC Saturday) to surrender their positions and return to their pre-June 2014 positions.

Turkey offers help against PKK

In a statement, the Turkish foreign ministry said on Monday it supported the Iraqi government in retaking control of Kirkuk, offering to aid Iraqi forces to oust Kurdish forces from the oil-rich city. "We are ready for any form of cooperation with the Iraqi government to end the PKK presence in Iraqi territory," the ministry said.

Baghdad said on Sunday fighters from Turkey's outlawed Kurdistan Workers' Party (PKK) were present in Kirkuk among Kurdish peshmerga forces, in what it said amounted to a "declaration of war."

Read more: In Iraq, minorities pin hopes on a Kurdish state

"It is impossible to remain silent" faced with "a declaration of war towards Iraqis and government forces," the National Security Council headed by the Iraqi prime minister said in a statement.

The PKK-affiliated ANF News Agency said its fighters had been called to mobilize and form a "defensive line to protect the people." The PKK has close ties with some Iraqi Kurdish parties, particularly the Patriotic Union of Kurdistan. Turkey's offer also stems from its support for its ethnic cousins, the Turkmen, which reside in the Kirkuk province.

Kirkuk: In Kurdish hands since 2014

Abadi has demanded that Kurdish leaders disavow the September 25 referendum, but the Kurds have rejected the demand. Baghdad called the referendum "anti-constitutional." Turkey, Iran and the United States were all against the vote.

After the referendum, the Iraqi parliament asked Abadi to use armed force to retake control of Kirkuk, which is inhabited by Kurds as well as Sunni and Shiite Turkmen and Arabs. Last week, Abadi said he would accept a "joint administration" with the Kurds in the province.

Read more: Opinion: Kurds find few friends in independence referendum

The Kurdish peshmerga have controlled Kirkuk since 2014, when it prevented the province's oil fields from falling into the hands of IS after the Iraqi army collapsed. With Baghdad weak, the Kurds moved to expand territory under their control outside the three provinces that officially make up the Kurdistan region.

The Kurds and Baghdad have long been in dispute over oil resources and revenue sharing. But the apparent collapse of the peshmerga within a day also led to bitter accusations between rival Kurdish parties, the Patriotic Union of Kurdistan and Barzani's Kurdistan Democratic Party, highlighting factionalism that has plagued the Kurdish camp.

US 'not taking sides'

US President Donald Trump said on Monday that the US was not taking sides in the conflict. "We don't like the fact that they're clashing. We're not taking sides," Trump told reporters at the White House.

"We've had for many years a very good relationship with the Kurds as you know and we've also been on the side of Iraq," he
said.

Kurdish government representative in Washington, Bayan Sami Abdul Rahman, said the US had already helped isolate the Kurds by publicly calling for them to postpone the September 25 referendum on independence that staretd the current dispute with Baghdad.

"With every step (Washington) emboldened Baghdad, Iran and Turkey ... each one of them thinking: 'Well, so the Kurds are on
their own, we can do whatever we like'," she told the news agency Reuters.

 
ls, cw/rt/jbh (Reuters, AFP, AP)