At least 37 people were killed in an explosion in the Turkish capital Ankara on Sunday, according to Turkey's health minister.
The health minister also said 125 people were being treated at hospitals, of which 19 are in serious condition.
The blast occurred near the central Guven Park, close to a major transportation hub.
NTV television says the bomb exploded Sunday near a park at Ankara's main square. Several cars caught fire.
Several ambulances and police cars were sent to the scene, an area close to government offices and ministries.
Prime Minister Ahmet Davutoglu was convening an emergency security meeting. In a statement, President Tayyip Erdogan said the bombing will only bolster Turkey's resolve in fighting terrorism and it will never give up the right to defend itself. He also said terrorist organizations were targeting civilians because they were losing their struggle against security forces.
The explosion was caused by a car bomb going off near a bus stop, said the Ankara governor's office in a statement.
A senior security official says the blast appears to have been a suicide car bombing.
The 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, an offshoot of the outlawed rebel group the Kurdistan Workers' Party, or PKK, claimed responsibility for the Feb. 17 attack.
"Deeply saddened and horrified by attack in Ankara. We extend our deepest condolences to victims & their families" pic.twitter.com/oGmWzuU08N— @USEmbassyTurkey
European leaders condemned the bombing. British Prime Minister David Cameron said he was "appalled". French Foreign Minister Jean-Marc Ayrault described it as a "cowardly attack".
U.S. State Department Spokesman John Kirby on Sunday conveyed condolences to the families of those killed Sunday and wished a quick recovery for the wounded.
"We reaffirm our strong partnership with our NATO ally Turkey in combating the shared threat of terrorism," he said.
Turkey blames PKK for Sunday explosion
An official told Reuters that PKK may be behind Sunday's explosion.
"According to initial findings, it seems that this attack has been carried out either by the PKK or an affiliated organization," the official said.
Sajjan Gohel, international security director for the Asia-Pacific Foundation, an independent think tank specializing in global security, told CBC News in a televised interview that PKK attacks have been an "ongoing issue" for the Turkish state.
"The Turkish state has been at odds with the PKK for many decades now," he said, adding the PKK has carried out attacks against Turkey before. "This has been an ongoing issue."
Gohel said the PKK's actions are motived by separatist sentiments, which have grown in recent years.
"The PKK has always wanted a separate state for the Kurds in southern Turkey and this is perhaps gained momentum in the last few years," he said.
"The Turkish government are very quick to blame the PKK and it may well prove to be true."
Sunday's attack also came two days after the U.S. Embassy issued a security warning about a potential plot to attack Turkish government buildings and housing in one Ankara neighbourhood and asked its citizens to avoid those areas.
Court bans Facebook, Twitter
An Ankara court ordered a ban on access to Facebook, Twitter and other sites in Turkey on Sunday, after images from a car bombing in the Turkish capital were shared on social media, broadcasters CNN Turk and NTV reported.
Several local users reported difficulty in accessing the sites.
Turkey last year blocked access to Twitter over the sharing of photographs of a prosecutor being held at gunpoint by far-left militants.