As advancing troops, backed by fighter jets, closed in on a main rebel base in rugged mountains near the Turkish border, Iraq's government condemned the incursion as a violation of the country's sovereignty.

"The cabinet in a meeting today expressed its rejection and condemnation of the Turkish military incursion, which is considered a violation of Iraq's sovereignty," said a government statement issued in Baghdad.

The condemnation came shortly after Erdogan said in Ankara that Turkey was exercising its right to self defence against the separatist Kurdistan Workers' Party (PKK). The PKK is listed as a terrorist organization by Turkey, the United States and the European Union.

"Turkey's cross-border operation is a result of its legitimate right to self-defence," Erdogan said in a televised speech.

"Turkey is in a rightful struggle against the terrorist organization that is threatening regional peace and stability."

Turkish forces stormed into the autonomous Kurdish-run north of Iraq Thursday to fight an estimated 4,000 PKK rebels.

Ankara accuses them of using the region as a springboard for attacks in their 23-year armed separatist campaign in southeast Turkey, which is just over the border.

Iraq and the United States have issued repeated calls for the incursion to be wrapped up as swiftly as possible, so as to avoid destabilising one of Iraq's relatively stable areas.

Over the weekend US Defense Secretary Robert Gates, who is expected to fly to Ankara Wednesday, urged Turkish authorities not to keep their struggle against the rebels limited to military means.

Turkey says it will withdraw its troops once they achieve their objective of flushing out the rebels and destroying their camps, but has given no timeframe.

But Erdogan argued that the PKK presence was a source of "political instability" for Baghdad and gave fresh assurances that Turkey's military action had no aim other than routing the rebels.

"This operation is not against northern Iraq but only against the terrorist organization... Turkey has always supported the protection of Iraq's territorial integrity, sovereignty and political unity," he added.

The Turkish army says it has so far killed 153 rebels and lost 17 soldiers since the beginning of the incursion.

The PKK, whose campaign has claimed more than 37,000 lives since 1984, claims to have killed 81 soldiers and to have shot down an attack helicopter.

Roj-TV, a Denmark-based Kurdish channel, which Ankara says is a mouthpiece of the PKK, on Tuesday broadcast what it said were images of the helicopter's wreckage.

The Turkish army has said one of its helicopters was "destroyed" but gave no details.

Regional security forces in northern Iraq on Tuesday reported sustained fighting overnight as Turkish soldiers advanced on a PKK base in Zap area.

The camp, situated in a deep valley just a six-kilometre (four-mile) walk from the Turkish border, has been identified by the military as a major staging post used by the PKK to launch attacks into Turkish territory.

Clashes continued in the mountainous Hakurk area to the east, close to Iraq's border with Iran, where the Turkish army air-dropped troops and helicopter gunships pounded rebel positions on Monday.

PKK fighters suffered "heavy losses under fire from close quarters" as they tried to escape the advancing Turkish columns, the general staff said in a statement Monday.

The operation was condemned by the country's main Kurdish political movement, the Democratic Society Party, as a "war" and a move that would antagonise Turkey's restive Kurdish community.

"We see the operation as a decision that will make it difficult to live side by side," senior party member Ahmet Turk said.