Iraq's oil-rich Kirkuk province voted on Tuesday to participate in a Kurdish independence referendum scheduled for September, in a move that could raise tensions in the disputed region.

The ethnically mixed province of Kurds, Arabs and Turkmen has long been at the center of disputes between Baghdad and the autonomous Kurdistan Regional Government (KRG).

Iraq's Kurds plan to hold a non-binding independence referendum on September 25 in three northern provinces that make up the autonomous Kurdistan region.

Controversially, the vote also includes so-called disputed areas outside the KRG's official boundaries, captured when the Iraqi army crumbled in 2014 as the so-called "Islamic State" (IS) swept through the country.

Read more: The Middle East's complex Kurdish landscape

Arab, Turkmen boycott

Only 24 of the Kirkuk provincial council's 41 members attended Tuesday's vote, with 23 voting in favor of joining the referendum. Arabs and Turkmen boycotted the vote.

Kirkuk's Kurdish governor Najmaldin Karim told reporters after the vote that it represented a "historic event."

"We have the right to take part in the referendum, and whoever denies this knows nothing about human rights," he said.

Iraq's central government strongly opposes the referendum, especially the inclusion of disputed territories outside official KRG borders.

Iraqi Prime Minister Haider al-Abadi has denounced the Kirkuk decision, with government spokesman Saad al-Hadithi saying the vote was "illegal and unconstitutional."

"Provinces that don't belong to the autonomous region [of Kurdistan] can't impose decisions without the federal government's approval, and Kirkuk is one of these regions," Hadithi said.

Ethnic powder keg

The decision adds to already long-running disputes with Baghdad over Kurdish oil exports and revenue sharing.

Sunni MP Mohammed al-Karbouli told Reuters that the Kirkuk issue "would help trigger ethnic fighting" and "extend the life" of the "Islamic State."

The United States and Western governments including Germany oppose the Kurdish referendum, arguing it will undermine the fight against IS and create potentially explosive tensions with Baghdad.

Turkey and Iran have also opposed the referendum out of fear it could have a knock-on effect on their own Kurdish minorities.

Turkey said the Kirkuk decision was a "mistake" and a violation of the Iraqi constitution.

"Insisting on pursuing this dangerous course will not serve the interest of [the autonomous Kurdish region] or of Iraq, it will not be accepted by the international community, and will not contribute to regional peace and stability," the Turkish Foreign Ministry said in a statement.

Turkey has close economic and political relations with the KRG and its president, Masoud Barzani. It also holds considerable leverage over the KRG due to Turkey being the only major outlet for Kurdish oil exports.

At the same time, the status and rights of Turkmen, ethnic cousins of Turks, is a highly charged issue among Turkish nationalists.

Kurdish infighting

The referendum will occur amid deep divisions between Kurdish political parties and questions over the leadership of Barzani, who was supposed to step down three years ago at the end of his two terms as president before receiving a controversial extension. The KRG parliament has been shuttered since 2015 over political infighting.

Read more: Who are the Kurds?

Analysts say the referendum is unlikely to lead to an immediate declaration of independence and is designed, for now, to bolster the Kurds' bargaining position with Baghdad over disputed territories, shared oil revenues and greater autonomy.

Kirkuk province has long been at the center of disputes between Baghdad and the Kurds.

The province underwent "Arabization" under former Iraqi dictator Saddam Hussein, shifting the demographic balance of the province that was once majority Kurdish. 

Since the 2003 US invasion of Iraq, Kurds have sought to tip the demographics of the province back in their favor.

Under article 140 of Iraqi's constitution, Kirkuk is supposed to hold a referendum on its status but the vote has been repeatedly delayed.

cw/cmk (AFP, AP, dpa, Reuters)