The Kurdistan Freedom Falcons (TAK), a faction of the banned Kurdistan Workers' Party (PKK), claimed responsibility on its website for a car bombing in central Ankara at the weekend that killed 37 people.
TAK was also behind a February 17 bombing in Ankara that targeted a military convoy, killing 30 people including the attacker.
A two-year ceasefire between Turkey and the PKK collapsed in July amid mutual recriminations and a collapse of peace talks. The Kurdish militants, who have been fighting the state for three decades, are demanding greater autonomy and right for the minority group.
The state stepped up military operations against the PKK and other groups in December.
TAK is seen as a splinter that broke away from the PKK more than a decade ago, though some security experts claim there are still links.