Istanbul (dpa) - At least 27 people have been killed and 75 wounded in a car bombing Sunday in the heart of the Turkish capital, CNN Turk reported citing the governor of Ankara.

The blast took place in the central area of Kizilay Square at a bus stop and most of the casualties were feared to be civilians, according to local media reports.

Broadcaster NTV said it was a car bomb.

Broadcast footage showed several fire trucks and ambulances rushing to the scene. The bomb reportedly went off near the Education Ministry, Hurriyet Daily News said online.

On Friday, the US embassy in Ankara warned of a "potential terrorist plot to attack Turkish government buildings and housing located in the Bahcelievler area of Ankara." That area is 3 kilometres away from Sunday's blast site.

There was no immediate statement from the Turkish government, which imposed a media blackout on the attack.

Sunday's explosion comes weeks after a bombing in February in Ankara that targeted a military convoy and killed 30 people, including the attacker.

A Turkish armed splinter group, the Kurdistan Freedom Falcons (TAK), claimed responsibility for that attack.

Their claim countered the government's allegations that Syrian Kurdish allies of the United States were behind the attack.

In January, a suicide attacker killed 12 German tourists in central Istanbul. The Turkish government said the extremist militia Islamic State was responsible for that attack.

A twin suicide bombing in Ankara killed 100 people in October and was blamed on the Islamic State extremist group.