The outlawed Kurdistan Workers' Party, PKK, is denying responsibility for a bombing that wounded at least 32 people in the heart of Istanbul.
The pro-PKK news agency Firat says the group, which has been fighting for decades for autonomy in Turkey's Kurdish-dominated southeast, was not involved in Sunday's suicide bombing in Turkey's economic capital.
The bomber targeted a bus full of police officers, but about half of the wounded were civilians. Few suffered serious injuries.
The head of Istanbul's security forces, Oguz Kahn Koksal, says officials are investigating the bombing. No group has claimed responsibility.
Kurdish rebels, leftist extremist and Islamists have all carried out attacks in Turkey.
The attack took place on the same day that a unilateral cease-fire with Kurdish rebels was set to end. But the PKK said in Firat news Monday it has extended the ceasefire until the country's general elections next year.
The scene of the attack, Taksim Square, is a major tourist area, dominated by hotels, restaurants and shops. It is also home to the Republic Monument, built in 1928 to commemorate the creation of the Turkish republic.
Turkish Prime Minister Recep Tayyip Erdogan was visiting the Kurdish town of Mardin when the bombing occurred. He said his government will not tolerate those attacking the peace, stability and security of Turkey.