By Jim Muir
BBC News, Baghdad
The Turkish military incursion into northern Iraq has apparently turned out to be on a considerably lesser scale than initial reports had suggested.
The operation along the rugged, snowbound border is limited
Iraqi Kurdish officials and US-led coalition sources said only a few hundred Turkish troops at most took part in the cross-border operation.
The Iraqi Kurds - always on the look-out for any Turkish move that might be construed as an attempt against their own autonomous region - said the incursion took place in a remote, rugged and unpopulated sector of the border, where heavy snows hamper movement at this time of the year.
Iraqi Kurdish Peshmerga forces, who control the part of northern Iraq south of the Turkish border, had no contact with the Turkish troops and were only aware of the operation from monitoring military radio traffic.
No vehicles or tanks were involved in the move across the border, although helicopter gunships were in action as well as jets and artillery.
Iraqi Foreign Minister Hoshyar Zebari - himself a Kurd - described the operation as "very, very limited".
But he added that the Turks had destroyed five bridges over the Blue River tributary - part of the Greater Zaab river complex - and said he had called in the Turkish charge d'affaires in Baghdad to deliver a protest note.
Protective US umbrella
The underlying situation in Iraqi Kurdistan and on the Turkish border is so sensitive and tense that any news of Turkish military action is often blown out of proportion.
Turkish military statements are usually scant and elliptical, leaving the field open to speculation and interpretation.
But Ankara is well aware of Iraqi Kurdish sensibilities, and also that the United States is committed to maintaining the integrity both of Iraq as a whole, and of the federal autonomous region of Iraqi Kurdistan, which has enjoyed a protective US umbrella since the early 1990s.
Tensions were particularly high in October and November, when the Kurdistan Workers' Party (PKK) carried out raids in which about 30 Turkish soldiers were killed.
Turkey massed tens of thousands of troops on the border, a build-up which is still in place.
The Iraqi Kurds feared that a major invasion was imminent, and that their own autonomy would be the real target.
But the invasion did not materialise, with Washington playing a key role in persuading the Turks to hold off in exchange for co-operation in efforts to deal with the PKK with pin-point operations.
Washington confirmed that it had been notified in advance of the latest Turkish move, and received assurances that it would be directed solely at positions or fighters of the PKK.
Prime Minister Erdogan said the PKK threatens Turkey's integrity
They have hideouts in the rugged border mountains, from which they have conducted attacks across the border into Turkey.
The Turkish President, Abdullah Gul, also called his Iraqi counterpart, Jalal Talabani, on Thursday evening to assure him that border operations would not be directed against the Iraqi Kurds.
Mr Gul invited Mr Talabani, who is a Kurd, to pay an official visit to Ankara, an invitation which the Iraqi president accepted.
But the launching of the Turkish operation was preceded by some friction on the ground between Turkish troops and the Iraqi Kurdish Peshmerga forces.
There are two fixed Turkish bases inside northern Iraq, at Bamarni and Bakoufa, where a limited number of troops and tanks have been stationed since 1997 with a static monitoring and intelligence function.
On Wednesday, according to senior Iraqi Kurds, Turkish troops tried to move out of the bases to set up checkpoints on nearby main roads.
The PKK wants a Kurdish homeland in south-eastern Turkey
They were confronted by Peshmerga fighters who took up combat positions. There was a tense stand-off before the Turkish forces returned to their bases without any shots being fired.
The subsequent cross-border raid, so far at least, has fallen far short of the major incursion that had been feared before the winter weather ended the fighting season in late November.
For thousands of troops to pour across the border, as initial reports suggested, they would have to use the only major crossing, at Habur, near Zakho in the far north-west of Iraq.
The Iraqi Kurds say that did not happen. They control the southern end of the crossing, and would be the first to notice - and probably confront - a major Turkish advance.
Operations elsewhere along the rugged, snowbound border would necessarily be of a much more limited nature, until the spring thaws make the remote terrain somewhat more accessible.