There was no immediate claim of responsibility for the abduction.
Last year 46 Turkish citizens were seized by Islamic State militants in Mosul, but were released unharmed after more than three months in captivity.
Shi’ite militias and other armed groups also remain active in Baghdad.
Two police sources said the gunmen wore military uniforms and arrived in a convoy of black sports-utility vehicles. Maan denied reports that up to three Iraqis were also taken from the site, where workers were building a small sports pitch.
An Islamic State statement released last month accused Turkish President Tayyip Erdogan of “selling the country to crusaders” and of allowing U.S. access to Turkish bases “just to keep his post”. Ankara has taken a frontline role against the Islamist fighters pressing on its southern border.
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