The three had traveled to Turkey's most populous city from the south-east of the country, where armed Kurds have stepped up attacks this year in their fight for self-rule, planning to carry out attacks on civilians, Anatolia reported, quoting police.

Explosives and documents linked to the rebel Kurdistan Workers' Party (PKK), listed as a terrorist group by Ankara and much of the international community, were found during the police operation in which the three were arrested.

The detainees are also suspected of involvement in a bombing near a McDonalds fast-food restaurant on the European side of Istanbul on June 10 that injured 14 people, the news agency reported.

The PKK took up arms for self-rule in Turkey's Kurdish-majority southeast in 1984. The conflict has claimed more than 37,000 lives.