Thirty-four people were killed and 125 were injured during an attack in the Turkish capital of Ankara, said the country's health minister, Mehmet Muezzinoglu.
Thirty of the victims were declared dead at the scene; the remaining four died at hospitals, the minister said, adding that 19 of the injured remain in critical condition.
The blast, which local media attributed to a car bomb, occurred on the city's main boulevard, Ataturk Bulvari, close to Ankara's main square, Kizilay.
The private NTV news channel said a car, believed to be laden with explosives, detonated close to a bus.
Several vehicles then caught fire, the station said. The area is close to government offices, including ministries.
The deadly explosion — the third in the city in five months — came just three weeks after a suicide car bombing in the capital targeted buses carrying military personnel, killing 29 people.
A Kurdish militant group which is an offshoot of the outlawed Kurdish rebel group, the Kurdistan Workers' Party, or PKK, claimed responsibility for the Feb. 17 attack.
Turkish President Recep Tayyip Erdogan said Sunday that "terrorist organizations" were targeting "innocent civilians in the most immoral and heartless way" — and he promised to bring "terror to its heel."
"Our state will never give up its right to self-defense against all kinds of terror threats," he said, according to Turkey's state-run Anadolu Agency.
Two days before Sunday's attack, the U.S. Embassy in Turkey issued a warning "regarding a potential terrorist plot” to target government buildings and housing located in the Bahcelievlera section of Ankara, approximately three miles west of the deadly explosion.
American citizens were advised to stay away from the area.
On Sunday, British Prime Minister David Cameron said he was "appalled by the devastating terror" in Ankara and Ivory Coast, where at least 16 people — including four Europeans — were killed by gunmen at a popular beach resort.
In a statement, the U.S. Embassy in Turkey offered condolences to the victims and said it was "deeply saddened and horrified by the attack."