An Iraqi soldier was killed in clashes with gunmen as security forces searched for a suspect behind the kidnappings of 18 Turkish workers, the military said Friday.

The Turkish employees of construction company Nurol Insaat were seized Wednesday in the Sadr City area of north Baghdad, where they were working on a football stadium project.

Intelligence information had located "one of the members of the gang that carried out the kidnappings" in Baghdad's Palestine Street, the security command responsible for the capital said.

"Forces moved to search and inspect in Palestine Street, but were fired on by armed men who tried to intercept them, resulting in the martyrdom of a soldier and the wounding of three others," it said of the overnight operation.

It did not identify the gunmen, but Al-Etejah television station, which is affiliated with Ketaeb Hezbollah, said one of the Shiite militia's facilities had come under attack.

A Ketaeb Hezbollah source was quoted as saying the Baghdad Operations Command had targeted a Ketaeb Hezbollah headquarters in a raid on Palestine Street.

The Islamic State jihadist group has kidnapped dozens of Turks in northern Iraq over the past 18 months and later released them, but the latest abductions took place in Sadr City, a stronghold of Shiite paramilitary forces.

Baghdad turned to mostly Shiite volunteer forces for support as IS advanced towards the capital in June last year, and they have played a key role in halting and then reversing the jihadists' gains.

But in doing so, the Iraqi government empowered Shiite militias, some with chequered human rights records, and spurred the creation of new ones, allowing them to act with near-impunity despite them officially falling under government command.

Some fighters linked to the militias stand accused of criminal activities, including kidnappings as well as property seizures and murders.

Kidnappings for ransom are a persistent problem in Baghdad, although political motives are also possible.

Ankara has been accused of complacency towards IS and complicity in assisting the jihadist group, which also holds substantial territory in common neighbour Syria.

Turkey backs the mostly-Sunni rebel forces battling to overthrow Syrian President Bashar al-Assad, while Iraqi Shiite forces have fought alongside his regime.