The Iraqi foreign ministry has summoned the Turkish ambassador to demand that Turkey withdraw troops it sent to an area near the northern city of Mosul.
It said the troops had entered Iraq without Baghdad’s consent and that Iraq considered it “a hostile act”.
Turkey says it deployed 150 soldiers in the town of Bashiqa to train Iraqi Kurdish forces fighting the Islamic State (IS) group.
Mosul has been under the control of IS militants since last year.
Turkish Prime Minister Ahmet Davutoglu described the deployment as a routine troop rotation. He said Turkish forces had set up a camp near Mosul a year ago in co-ordination with Iraq.
“This camp was established as a training camp for a force of local volunteers fighting terrorism,” he said.
Earlier, Iraqi Prime Minister Haider al-Abadi’s office said the move was a “serious breach of Iraqi sovereignty”.
The statement called on Turkey to “respect good neighbourly relations and to withdraw immediately from the Iraqi territory”.
Turkey enjoys close relations with autonomous Kurdish regions in Iraq, although it views Syrian Kurdish groups over the border as hostile, analysts say.
The fall of Mosul was a key moment in the rise of IS and a Iraqi government offensive to retake the city has been repeatedly put back.
This week saw the UK carry out its first air strikes against IS in Syria and Germany voting to send military support to the coalition fighting IS in the country.