Turkish planes have for the first time carried out air strikes against Islamic State (IS) group targets in Syria.
Prime Minister Ahmet Davutoglu said the air strikes, on three IS positions, "completely destroyed" their targets.
On Thursday, Turkish forces exchanged fire with IS fighters near the Syrian border. One Turkish soldier was killed.
In the early hours of Friday, police launched raids against IS and Kurdish militants across the country, arresting 297 people.
In Istanbul, more than 5,000 officers helped search 140 properties.
Members of the youth wing of the outlawed Kurdistan Workers' Party (PKK) and of a far-left group, the Marxist Revolutionary People's Liberation Party Front (DHKP-C), were also arrested.
The state-run Anadolu news agency said there were also arrests in the cities of Ankara and Izmir and in Sanliurfa province, near the Syrian border.
Turkish President Recep Tayyip Erdogan said the operations against militants would continue.
The arrests come after the PKK's military wing said it killed two Turkish police officers on Wednesday. The group claims the men collaborated with IS in the bombing of a Kurdish activists' group on Monday that killed 32 people.
Separately, Turkey said that F-16 jets had hit three IS targets in Syria.
It is the first time Turkey has confirmed air strikes against targets in Syria since IS began its advance through Iraq and Syria in 2013.
Turkish state TV said that the jets had not violated Syrian air space as they attacked the border village of Havar, next to the Turkish town of Kilis.
The US is expected to step up bombing raids against IS after reaching an agreement with Turkey to use the Incirlik airbase.
The agreement was finalised in a phone call between President Barack Obama and Mr Erdogan on Wednesday. It was confirmed by US officials speaking on condition of anonymity.
Analysis - Jonathan Marcus, BBC diplomatic and defence correspondent
Turkey appears to have dropped its studied ambivalence towards IS and has weighed in with air strikes and the shelling of IS targets in Syria, as well as a wave of arrests of IS sympathisers at home.
More important still could be the decision by Ankara to allow US warplanes to strike IS targets from its base in Incirlik.
This provides vital airfields much closer to IS targets in Syria and could enable a step-change in the US air campaign.
For too long, many in the West have argued, Turkey prioritised the removal of the Syrian leader Bashar al-Assad and its own turbulent relations with the Kurds rather than seeking the demise of IS.
But Islamic State may well have over-played its hand, demonstrating that it represents a clear security threat to Turkey which Ankara can no longer ignore.
The air raids on Syria come after a bloody few days on the Turkish side of the Syrian border.
- On Monday, 32 people were killed in a bombing in the predominantly Kurdish town of Suruc - IS were blamed
- On Thursday, Kurdish militants said they killed two police officers in the city of Celanpinar as retaliation, accusing the policemen of collaborating with IS
- Also on Thursday, IS fighters attacked a Turkish border post near Kilis - Turkey's army retaliated, killing one of the militants
The Turkish government has faced criticism at home and abroad for not doing enough against IS, despite being part of the international coalition fighting it.
A return to Incirlik
The US military is more than familiar with the southern Turkish base, and its recent history is tied closely with recent US military operations.
- During the first war against Iraq in 1990, US planes were stationed at the base
- Humanitarian operations for Kurdish refugees flew out of Incirlik after the war
- The base also served as the main hub for operations at the start of the war in Afghanistan in 2001
- It acted as the first stop on the way home for thousands of US troops leaving Iraq after the 2003 invasion
- Wikileaks claimed the US and Turkey allowed the base to be used to launch rendition flights for terror suspects
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