Turkish anti-terror police have raided more than 100 suspected Islamic State and Kurdish militant group locations in Istanbul, in an overnight operation.
The operation, supported by helicopters and special forces, deployed 5000 police officers in 26 districts of the city. They arrested 251 people linked to IS, the office of Prime Minister Ahmet Davutoglu said.
Members of the youth wing of the outlawed Kurdistan Workers' Party (PKK) and of a far-left group 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.
The action follows Monday's deadly suicide attack in the Syrian border town of Suruc, which killed 32 young activists.
There were violent clashes across Turkey as hundreds of protesters took to the streets to condemn the attack in Suruc and accused the government of not doing enough to combat the threat of IS.
Suruc is home to many refugees who have fled fierce fighting between IS and Kurdish fighters in nearby Kobane.
Western states have also accused Turkey of not doing enough to halt the rise of the group, but the country has taken a harder line against it in recent weeks.
Mr Davutoglu's office also said that F-16 jets had hit three IS targets in Syria.
It is the first time Turkey has launched air raids against targets in Syria since IS began its advance through Iraq and Syria in 2013.
On Thursday, Turkish forces exchanged fire with IS fighters near the Syrian border. One Turkish soldier was killed.
Turkey will now let the United States launch air strikes against IS from the Incirlik air base, US officials have said.
-BBC / Reuters