— Iraqi Kurds seized control of two oil fields Friday, vowing to use the oil to meet Kurdish consumption needs and raising tensions between the country’s political and ethnic factions as they struggle to form a new government.

The Kurdistan Regional Government (KRG), which governs a largely autonomous region in northern Iraq, said Kurdish forces moved into two northern oil fields Friday morning to preempt what it alleged were orders by the government in Baghdad to “sabotage” a new pipeline that would be used to export oil via Kurdish territory.

Iraq’s Oil Ministry accused the Kurds of seizing the Bai Hassan and Kirkuk-area oil fields in violation of Iraq’s constitution.

“They are ignoring the government of Baghdad, and they are threatening the unity of Iraq,” said Assem Jihad, a ministry spokesman.

Kurdish authorities built the pipeline in recent years, without Baghdad’s assent, but had not put it to use. Since Sunni militants swept into northern Iraq last month, rendering a critical stretch of oil infrastructure inoperable, bringing the new pipeline into service has become imperative, the regional government said in a statement.

“From now on, production at the new fields under KRG control will be used primarily to fill the shortage of refined products in the domestic market. This will ease the burden on ordinary citizens caused by the failure of the federal authorities to protect the country’s vital oil infrastructure in the region,” the regional government said.

The Iraqi government is concerned that the Kurds, who have vowed to push forward with a referendum on their region’s independence, will seek unilaterally to sell oil pumped from the Kirkuk fields.

Kurdish forces consolidated their control of the contested city last month after Iraqi forces fled the area in the face of advancing Sunni militants from the Islamic State.

The jihadists now control an enormous swath of territory between the Kurdish semiautonomous region in the north and southern provinces still under the control of the Iraqi government.

The conflicting allegations between the central government and the Kurds on Friday highlight Baghdad’s growing isolation as the country edges closer to fracturing into what some analysts describe as a Kurdish region, a Sunni region and a Shiite region.

On Wednesday, Iraqi Prime Minister Nouri al-Maliki, a Shiite, accused the mainly Sunni Kurds of collaborating with the Islamic State by harboring terrorists in the Kurdish capital, Irbil. He also halted all cargo flights into Iraqi Kurdistan.

The Kurds responded Thursday by withdrawing their ministers from Maliki’s cabinet.

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On Friday, Maliki appointed five new ministers to replace the Kurds, the Associated Press reported. The appointments included a Shiite replacement for Foreign Minister Hoshyar Zebari, a Kurd.

Kurds, Sunni Arab leaders and also some of Maliki’s former Shiite allies have increasingly urged Maliki to step down as prime minister. Critics accuse Maliki of running a sectarian government that isolated Sunnis and contributed to the eruption of Iraq’s current crisis.

Sectarian killings have been on the rise in the past month.

Human Rights Watch said Friday that Iraqi security forces and affiliated militias appear to have executed more than 250 Sunni prisoners — a war crime — since the Sunni militants launched their assault in northern Iraq last month.

The group said it had collected evidence of five prison massacres between June 9 and 21, most of them occurring as Iraqi security forces fled the Islamic State’s offensive.

If the killings were carried out on a systematic scale or were sanctioned by the government, they would amount to a crime against humanity.

On Friday, Iraq’s top Shiite cleric, Grand Ayatollah Ali Sistani, called on Iraqi fighters to respect the rights of all Iraqis, regardless of sect, in an apparent effort to quell the bloodshed.

Sunnis have accused Sistani of inflaming sectarian tensions with his call in June for Iraqis to take up arms against the Sunni militants.Thousands of Shiite volunteers have heeded his call, joining Shiite militias and heading to the country’s front lines.

Khalid Ali contributed to this report.