A Kurdish militant group has claimed responsibility for a suicide car bomb attack in the Turkish capital which killed 37 people.

In a statement posted Thursday on its website, the Kurdistan Freedom Falcons (TAK) said the attack in Ankara was in response to Turkish military operations against Kurdish rebels in the southeast.

TAK said it had not intended to kill civilians and was targeting security forces. It said a large number of civilians had been killed after police intervened, without explaining exactly how, and warned that further civilian deaths were "inevitable".

The Turkey-based group is considered an offshoot of the Kurdistan Workers' Party, or PKK, and has carried out several attacks in the past including one in Ankara in February that killed 28 people.

More than 200 people have died in five suicide bombings in Turkey since July that were blamed either on the Kurdish rebels or ISIS.

The increased violence in Turkey has also put strain on the NATO member's relationship with the United States, which is supporting a Syrian Kurdish militia, the YPG, in the fight against ISIS in Syria. Turkey says the Syrian Kurdish fighters have links to the PKK. Washington considers the PKK a terrorist group, but not the YPG.

Separately, Germany said it had closed its embassy in Ankara due to indications that an attack could be imminent. The consulate and German school in Istanbul were also closed, it said.

with files from Reuters