Turkish troops crossed into northern Iraq late Monday, heading towards Kurdish rebel bases in Haftanin valley, as warplanes bombed the area, local security sources said.
Some 20 tanks and 30 military trucks entered Iraqi soil from Siyahkaya village around 15 kilometers (eight miles) east of the Habur gate on the Turkish side of the border, sources said.
Turkish warplanes also bombed the Haftanin region where some 400 rebels are believed to be settled, they added.
Turkish troops were sent by helicopter to the Zap region, they said, adding that they aimed to enter Iraq's Sinaht region, which is close to Haftanin and where rebels of the Kurdistan Workers' Party (PKK) are thought to be based.
Firatnews news agency, known as the mouthpiece of the PKK, confirmed Monday that Turkish troops had entered Iraq from the Siyahkaya region.
Turkish soldiers erected drawbridges on Hezil river in the region, Firatnews said.
The Turkish military launched air and land operations against the PKK after the separatist group's guerrillas killed 24 soldiers and wounded 18 along the Iraqi border on Wednesday, the army's biggest losses since 1993.
Some 10,000 troops on the ground were involved in Turkey's operations, backed by jets and helicopters, inside Turkey and across the border. Military officials did not say how many troops had entered Iraq.
However, the army said the ground operations were mainly focused inside Turkey, around the Cukurca region near the Iraqi border.
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"A total of 49 terrorists were rendered ineffective" last week, the general staff said in a statement posted on its website Friday.
Turkey last week looked for support from its neighbours in its fight against the PKK.
Iranian Foreign Minister Ali Akbar Salehi met Friday with his Turkish counterpart Ahmet Davutoglu, urging "more serious cooperation" against the rebels.
Tehran has been carrying out a major offensive against the Party of Free Life of Kurdistan (PJAK), which Turkey considers a branch of the PKK, since July.
Already Thursday, Baghdad had pledged to cooperate with Ankara on security issues.
Nechirvan Barzani, a former prime minister of the Iraqi Kurdish regional government, offered his support during a surprise visit to Ankara Thursday, when he met Davutoglu and Prime Minister Recep Tayyip Erdogan.
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 for Kurdish independence in southeastern Turkey in 1984, sparking a conflict that has claimed some 45,000 lives.
Turkey's last ground incursion into northern Iraq, an autonomous Kurdish region, was in February 2008, when the army struck against the Zap region.