The Kurdistan Freedom Falcons (TAK), a splinter group of the Kurdistan Workers' Party (PKK), claimed Friday that it was behind this week's Istanbul car bombing, which targeted a police vehicle and killed 11, including six members of the security forces.
"We are again warning all foreign tourists who are in Turkey or wish to come to Turkey. Foreigners are not our target, but Turkey is no longer a safe country for them," TAK said in a statement on its website. It was issued in four languages.
The shadowy group - which dubbed Turkey a "fascist" and "colonial" country - said the attack was revenge for Turkey's military operations in Nusaybin, in the mostly Kurdish south-east.
The area has seen strict curfews repeatedly imposed since last year - when a ceasefire and peace process collapsed - and fighting between militants and the security forces has caused deaths and displacement.
In the Istanbul blast, which took place near the historic Grand Bazaar area popular with tourists, five civilians were killed, while 36 people were injured.
It was the third major blast in Istanbul this year, two of which were blamed on Islamic State. All have hit areas popular with tourists. TAK claimed two car bombings in Ankara this year that killed more than 60 people, including civilians and members of the security forces.
Tourism in Turkey has taken a sharp dive in recent months, owing to concerns about attacks and also due to Ankara's diplomatic row with Moscow, which heightened when Turkish forces downed a Russian plane near the Syrian border.
Tourism data last month showed a year-on-year drop of more than 28 per cent in the number of foreign visitors.
Security forces announced during the weekend that operations in Nusaybin ended, after nearly three months.
A few days later, a massive car bomb went off outside a police headquarters in a nearby district of Mardin province, killing six people. That blast, which used a suicide bomber, was claimed by the PKK itself.
A ceasefire and peace process with the PKK collapsed in July, leading to renewed fighting in a war that has been ongoing for more than 30 years, leaving more than 40,000 people dead. Turkey's government has ruled out a return to peace talks with the PKK, which it deems a terrorist group.
The new round of violence, which is largely focused on the mostly Kurdish south-east, has claimed many hundreds of lives, though some estimates say thousands have been killed.
Many Kurds in Turkey's south-east complain of systemic discrimination by the state, with demands for greater rights and autonomy.
Turkey is also using its air force in the conflict, launching strikes against alleged PKK targets inside the country and in northern Iraq.