Kirkuk (Iraq) (AFP) - Iraqi government forces, Shiite militiamen and Kurdish troops launched a large operation Thursday to free Amerli, a Turkmen town that has been besieged by jihadists for 50 days, officials said.

"The Iraqi army, (Shiite) volunteers and (Kurdish) peshmerga, equipped with heavy artillery and backed by the air force, have launched an operation to break the siege of Amerli and clear the neighbouring town of Sulaiman Bek," the mayor of neighbouring Tuz Khurmatu, Shallal Abdul Baban, told AFP.

He said four Shiite militiamen and two Iraqi soldiers had already been killed in the offensive, which began before dawn.

Abdul Baban also said 39 other Iraqi troops and volunteers, as well as four peshmerga, were wounded.

A regional security official and a peshmerga source confirmed the information.

The anti-jihadist forces were said to be only three kilometres (two miles) from Amerli, a town of 20,000 mainly Shiite Turkmen that has been completely surrounded by Islamic State militants since June 18.

For weeks, residents had appealed for a military intervention and warned that food, medication and water were in short supply.

It was not immediately clear how close the pro-government forces were to breaking the siege imposed by jihadists who had been controlling all 34 villages around Amerli.

For weeks, government forces had remained south of Amerli, apparently unable to push any further, and peshmerga forces had maintained positions in Tuz Khurmatu, apparently unwilling to move.

The string of setbacks suffered by the peshmerga in recent days and the federal forces' inability to regain the ground it lost when IS launched its major offensive two months ago have led to mounting domestic and international pressure for Baghdad and the Kurds to set aside their differences and cooperate on the ground.

Iraq's Turkmen minority, of Turkic ethnicity, is one of the country's largest and lives exclusively in the north. It is mostly Sunni Muslim but its Shiite component has been systematically targeted by jihadists over the past two months.