Turkish President Recep Tayyip Erdogan has hinted that his country will carry out a military operation in northern Syria in response to the deadly attack in Istanbul last Sunday.
The bombing killed six people, including two children, and wounded 80 in a busy shopping district.
Mr Erdogan said the attack was carried out by a Syrian citizen identified as Ahlam Al Bashir, who was trained in Kobani, a town in northern Syria under the control of Kurdish authorities.
The militant Kurdistan Workers' Party (PKK) has been blamed for the attack, but denies it was involved.
No group has yet taken responsibility.
“Turkey will do what is necessary in the light of investigations following the attack on Istanbul," Mr Erdogan said on Wednesday at the G20 summit in Indonesia.
“My country will continue to firmly implement its strategy to eliminate the threat of terrorism from its roots.
"Turkey expects all of its friends and allies to sincerely support the legitimate struggle in the fight against terrorists.”
Mr Erdogan and Turkish Interior Minister Suleyman Soylu said this week that the bomber was trained in northern Syria and that the attack was ordered from Kobani.
"I reiterate that there is no place for any form of terrorism in the future of our country and our region," Mr Erdogan said.
"The terrorist organisation of the Kurdistan Workers' Party is trying to cover up its defeats in Syria and Iraq with treacherous operations such as the bombing that took place in Istanbul last Sunday.
"This shows the bloody and ugly face of the terrorist group."
The PKK began an insurgency against Turkey in 1984 that has killed more than 40,000 people. The PKK has been designated as a terrorist group by Turkey, the US and the EU.
Turkey has carried out cross-border air strikes, often with armed drones, in Iraq and Syria as part of its offensive against Kurdish militants.
