Iraq's prime minister has said the semi-autonomous Kurdish capital of Erbil is becoming an operations base for the Islamic State group that has seized areas of northern and western Iraq.

Nouri al-Maliki said on Wednesday: "We will never be silent about Erbil becoming a base for the operations of the Islamic State and Baathists and al-Qaeda and the terrorists.

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His comments come days after the Kurdish president, Massoud Barzani, asked his parliament to plan a referendum on independence from the rest of Iraq. Kurdish forces have also taken over the city of Kirkuk when it was attacked by Sunni rebels.

Al Jazeera's Imran Khan, reporting from Baghdad, said Maliki's statement was unexpected, and could serve to divide Iraq further at a time when Sunni, Shia and Kurds were being urged to unite to face the threat of the Islamic State group. 

"It's likely he was referring to ‎the tribal Sunni sheikhs in Erbil who have been vocally critical of the prime minister and have said that they won't fight alongside the Iraqi army until he is out of office," said Khan.

"They blame him for the current crisis due to his government's sectarian policies."

Iraq's national parliament has failed to form a government, adjourning several times in the past two weeks, as it faces an Islamic State-led rebellion in the northern and western Sunni areas.

Corpses found

Maliki's comments also come after Iraqi security forces found 53 corpses, blindfolded and handcuffed, in a town south of Baghdad.

Officials said that the bodies had been left in the mainly Shia Muslim village of Khamissiya early on Wednesday, about 25km southeast of the city of Hilla, near the main highway running from the capital to the southern provinces.

The head of the provincial council, the local police and the governor's office all confirmed the discovery of the bodies, but had no immediate information on the identity of the dead, who appeared to have been killed execution style.

Fierce fighting between the rebels and the army, backed by Shia armed groups, has raised fears of a return to the sectarian bloodshed which peaked in Iraq in 2006 and 2007.

Sunni fighters have been carrying out attacks around the southern rim of Baghdad since the spring.

In response, Shia militias have been active in the rural districts of Baghdad, abducting Sunnis they suspected of terrorism, many of whom later turn up dead.

Meanwhile, at least seven people were killed in air strikes in the northern city of Mosul on Wednesday. Eight others have been injured in the attacks in western parts of the city.

Mosul, Iraq's second biggest city, has been under the control of Sunni rebels for nearly a month.

Source: Agencies