ANKARA: A car bombing in a busy square in central Ankara on Sunday killed at least 27 people and wounded 75 others, the provincial governor's office said.

“The blast was caused by a vehicle packed with explosives close to Kizilay square,” an official statement said. The square is a key commercial and transport hub close to the city's embassy area.

Ambulances rushed to the scene of the explosion on Kizilay square, a key hub in the city, and television pictures showed burnt-out vehicles including a bus.

A local news channel said the explosion occurred as a car slammed into a bus, suggesting that the blast may have been caused by a car bomb. Several vehicles had caught fire, it said.

Police sealed off the area and pushed onlookers and journalists back, warning there could be a second bomb.

Medical sources said the wounded had been taken to 10 different hospitals around the city, with a dozen said to be in a very serious condition.

Worst bomb attacks in Turkey

Following is a list of the worst bomb attacks in Turkey during the past three years:

• March 13, 2016: At least 27 people are killed and dozens wounded in acar bombing near Ankara's main Kizilay square.
• February 17, 2016: 29 are killed in a car bombing targeting theTurkish military in Ankara.
• January 12, 2016: 11 German tourists are killed and another 16 peoplewounded in a suicide attack by a Syrian bomber in Istanbul'sSultanahmet district.
• October 10, 2015: 103 people are killed and more than 500 wounded intwin suicide bombings targeting a pro-Kurdish peace rally in Ankara.
• July 20, 2015: 34 people are killed and about 100 injured in asuicide bombing in the predominantly-Kurdish town of Suruc near theborder with Syria.
• May 11, 2013: A twin car bomb attack kills 52 people in Reyhanli nearthe Syrian border. Ankara blames pro-Damascus groups.
• February 11, 2013: 17 people are killed when a Syrian minibusexplodes in Reyhanli.

The explosion shattered the windows of shops that line Kizilay square.

Dogan Asik, 28, said he was on a bus when the explosion occurred.

“We were thrown further back into the bus from the force of the explosion,” said Asik, who sustained injuries on his face and arm.

It comes just weeks after almost 30 people were killed in a car bomb attack targeting the military in the city on February 18.

Security threat

The Sunday's attack also came two days after the US Embassy issued a security warning about a potential plot to attack Turkish government buildings and housing in one Ankara neighborhood and asked its citizens to avoid those areas.

Coming so soon after the February bombing, the attack will raise fresh questions about Turkey's ability to manage the twin security threat posed by IS and Kurdish rebels, as Ankara presses the European Union to speed up its membership process in return for help with the migrant crisis.

The Kurdistan Freedom Falcons (TAK), linked to the PKK, said it carried out the February bombing in Ankara as revenge for operations by the Turkish military in the southeast of the country and warned foreign tourists not to visit the country.

A two-year ceasefire between the government and Kurdish rebels collapsed in the middle of last year and since December security forces have been waging a major campaign against the PKK in the southeast of the country.

Strict 24-hour curfews were imposed in a number of Kurdish-dominated towns and cities to allow the military and police to pursue the fight against fighters who had dug trenches and put up barricades.