Turkish jets kept up bombing raids on Kurdish rebel bases in northern Iraq overnight, as Turkey continued to look for support from its neighbours in its fight against the rebels on Friday.

Turkish warplanes continued to take off from Diyarbakir, the regional capital of the mainly Kurdish southeast, after the army's biggest losses at the hands of Kurdish rebels in 23 years, local security forces said.

The Turkish army said Friday that the air and ground strikes against the rebels are "mainly" in Turkey, with a "few" in Iraq.

"While the majority of the land and air operations are in (Turkey), mainly in the Cukurca region, ground and air strikes are ongoing in a few points in northern Iraq across the border," the army said in a statement posted on its website.

A small group of specially trained Turkish troops crossed into Iraq from the villages of Yekmal and Bilecan on the Turkish side of the border and entered the Dola Sulo region in Haftanin, the Kurdish news agency Firatnews quoted sources from the Kurdistan Workers' Party (PKK) as saying Thursday.

Gunshots and the sound of helicopters overhead were heard overnight in Cukurca, in Turkey's Hakkari province near the border, an AFP photographer in the city said.

He added that military helicopters flew from Cukurca to northern Iraq early Friday, while daily life in the town returned to normal after Wednesday's clashes left 24 soldiers dead and 18 wounded.

The Turkish army on Thursday initiated "a large-scale land operation" with 22 battalions against the rebels in five separate spots inside and across the border, according to the general staff. The ground incursion is supported with air strikes, it said.

Around 10,000 soldiers took part in the operation, Turkish media reported Friday. Some 6,000 of them were special forces, the daily Sabah said.

The battalions comprise commando units as well as gendarmerie and special forces, the army has said, without specifying how many had entered Iraq.

"The air and land operation is under way," Prime Minister Recep Tayyip Erdogan told reporters right after the military announcement.

Iranian Foreign Minister Ali Akbar Salehi met Friday with his Turkish counterpart Ahmet Davutoglu.

"Our first issue to discuss was terrorism. ... The PKK and the Party of Free Life of Kurdistan (PJAK) are the common problem of our countries," Salehi said afterward at a televised joint press conference with Davutoglu.

"The two countries should oppose those with ... more serious cooperation," Salehi said in translated remarks.

"Our joint determination to fight against PKK and PJAK will go on in its strongest terms," Davutoglu also said.

"From now on we will work together with a joint action plan until this threat of terror is eliminated totally," he said.

Salehi is also expected to meet with Erdogan and President Abdullah Gul, who said Turkey would exact "huge revenge" against the PKK for the attacks.

Iraq, in an official statement on Thursday, pledged to cooperate with Ankara on security issues.

Nechirvan Barzani, a former prime minister of the Kurdish regional government, who paid a surprise visit to Ankara on Thursday, said after meeting with Davutoglu: "We strongly condemn this attack." He also met with Erdogan.

The losses in a string of coordinated rebel attacks was the worst death toll for the army since 1993, when 33 unarmed soldiers were killed in Bitlis province.

Since July, Tehran has been carrying out a major offensive against PJAK, which Turkey considers a branch of the PKK.

Clashes between the PKK and the army have escalated since the summer.

The PKK, listed as a terrorist organisation by Turkey and much of the international community, took up arms in Kurdish-majority southeastern Turkey in 1984, sparking a conflict that has claimed some 45,000 lives.