An attack in Istanbul has all the hallmarks of Kurdish separatist group PKK, say Turkish security services.
Seventeen people died and more than 150 were injured in two explosions about 10 minutes apart in a working-class residential district.
No group has claimed responsibility, but officials say the attack may be in response to recent attacks on PKK bases by Turkish forces.
Television pictures showed ambulances carrying badly wounded people to hospital after the explosions at two different sites in the Gungoren district of Turkey's biggest city on Sunday.
Several groups, including the PKK, far-left groups and Islamic extremists, have carried out bomb attacks in Istanbul in the past.
Health Minister Recep Akdag says the death toll could rise further because seven people remain in a serious condition.
The blasts took place as the country's top court began deliberations on whether to ban Turkey's ruling party, the Justice and Development Party, or AKP, which is accused of violating the principle of secularism enshrined in the Turkish constitution.