Ankara says it is fighting a two-pronged "war on terror" against Islamic State (IS) jihadists in Syria and the PKK in northern Iraq, after a spate of attacks in the country.
But after initially targeting the IS group, the campaign has become increasingly focused on the PKK, with the Turkish air force bombing dozens of targets in an almost week-long campaign.
During the afternoon, 30 Turkish F-16 launched one of the heaviest raids yet in northern Iraq, hitting positions of the PKK in five locations, Turkish television reported.
The Hurriyet daily said Turkish intelligence sources believed as many as 190 PKK fighters had been killed in the air operations so far and 300 wounded.
But the government declined to give any toll. "This is not a football game but a fight against terrorism," a Turkish official told AFP.
The strikes have targeted camps and weapons stores used by the military wing of the PKK in the remote mountains of northern Iraq, including its headquarters on Kandil mountain. PKK targets inside Turkey's borders have also been hit.
The crisis erupted on July 20 when 32 people were killed in a suicide bombing blamed on IS jihadists in a town close to the Syrian border.
The PKK, who accuse Ankara of collaborating with IS, responded by murdering two Turkish police in their sleep and saying they no longer considered a ceasefire that had largely been observed since 2013 to be valid.
A peace process for a final settlement aiming to end the PKK's 30-year-plus armed uprising for more rights and powers for Turkish Kurds is now under severe strain.
- 'Case against Demirtas' -
The first shot was also fired in what may prove a long-running legal process against pro-Kurdish political forces, with prosecutors announcing a probe against against the pro-Kurdish Peoples' Democratic Party (HDP) leader Selahattin Demirtas.
Demirtas is accused of inciting people to take up arms during October 2014 protests that left dozens dead, the official Anatolia news agency said.
If the case comes to court, he could face up to 24 years in jail, it added.
Demirtas had accused President Recep Tayyip Erdogan of orchestrating the crisis in the hope of calling early elections to make up for the ruling party's lacklustre performance in June 7 polls.
Speaking earlier on a visit to China, Erdogan had told Demirtas to "know his place" and referred to the presence of his elder brother Nurettin among the PKK fighters in Iraq.
In an interview with AFP earlier, Demirtas dismissed the operations against IS as a "show" and said the real target was the PKK.
"A few air raids were launched by Turkey against IS targets for show only and it is over," he said.
The HDP's strong performance in the polls had prevented the ruling party winning an overall majority and frustrated Erdogan's dream of creating a presidential system with him at its head.
- Troops killed in PKK attack -
In apparent response to the air strikes, there has been a new wave of attacks on security forces in southeastern Turkey blamed on the PKK, with at least 11 police and army members killed since last week.
In the latest violence, three Turkish troops, including an officer, were killed when PKK militants opened fire on their convoy in the southeastern province of Sirnak, the army said.
Meanwhile, a Turkish policeman and a civilian were killed by a gun attack late Wednesday in the Cinar district of the mainly-Kurdish Diyarbakir region blamed on the PKK.
Funeral ceremonies for slain police and soldiers have now become an almost daily event, broadcast live on national television.
As well as the air strikes, Turkish security forces have also launched major operations to arrest suspected members of IS, the PKK and other militant groups including radical Marxists.
According to the latest figures, at least 1,302 people have been arrested so far with the vast majority of those detained suspected of links to the PKK.
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