A large number of Turkish fighter jets started launching strikes on Kurdish militants in northern Iraq during the past hours, days after President Tayyip Erdogan said a peace process had become impossible with Kurdistan Workers Party (PKK).

The strikes hit PKK targets including shelters, depots and caves in six areas, said Turkish media reports on Wednesday.

Military sources said nearly 200 PKK fighters were killed and scores of hideouts were destroyed.

Turkey launched near-simultaneous strikes against PKK camps in Iraq and the so-called Islamic State fighters in Syria last Friday, in what prime minister Ahmet Davutoglu has called a "synchronised fight against terror".

Turkey also opened up its air bases to the U.S.-led coalition against the so-called Islamic State, joining the front-line in the battle against the jihadists after years of reluctance.