Turkey early Wednesday launched a cross-border operation into the mountainous regions of northern Iraq where the Kurdistan Workers' Party (PKK), considered by Ankara to be a "terrorist" group, is thought to be hiding out.

Iraq's foreign ministry summoned Turkish ambassador Fatih Yildiz on Thursday and handed him a "strongly-worded memorandum calling for a halt to such provocative actions".

"We stress that Turkey must stop its bombardment and withdraw its attacking forces from Iraqi territory," the ministry said in a statement.

"We affirm our categorical rejection of these violations," it added.

It was the second time in a week that Baghdad summoned Yildiz, who was also called to the foreign ministry on Tuesday following Turkish bombardment in northern Iraq, also against PKK hideouts.

After that meeting, Yildiz said he had told Iraqi officials that if Baghdad did not take action against the rebels, Ankara would continue to "fight the PKK wherever it is".

The PKK has fought an insurgency against the Turkish state since 1984, using the rugged mountains of neighbouring northern Iraq as a rear base.

It has a tense relationship with the semi-autonomous Kurdish government in Iraq's north (KRG), which see the PKK as a rival but have been unable to uproot it from the area.

Analysts say the Turkish operation, dubbed "Claw-Tiger", could not have taken place without the KRG's tacit approval.

There has been no comment from Iraq's new Foreign Minister Fuad Hussein, himself a Kurd who is close to top KRG authorities.