The Kurdish militant group TAK says it carried out Sunday’s deadly attack in the Turkish capital, Ankara.
In an online statement it said the attack, which killed 37 people, was in revenge for military operations in the mainly Kurdish south-east.
The TAK, an offshoot of the banned Kurdistan Workers’ Party (PKK), had already said it was behind another bombing in Ankara last month.
Authorities in Turkey have blamed the latest attack on the PKK.
In a further development, Germany closed its embassy in Ankara and its consulate and a school in Istanbul on Thursday citing a “concrete threat” of an imminent attack.
Twelve German tourists were killed in a suicide bombing blamed on the so-called Islamic State (IS) group in Istanbul in January.
Sunday’s suicide car bombing took place in a busy commercial district and transport hub in the centre of Ankara. Dozens of people were wounded.
Analysis by Mark Lowen, BBC Turkey correspondent
After a bombing in 2011, TAK went quiet for a few years but has now reared its head with an attack at Istanbul’s Sabiha Gokcen airport in December and the two suicide bombings in Ankara.
The reason is clearly the resumption of armed conflict between the Turkish state and Kurdish militants in the south-east.
Since a ceasefire between the two sides collapsed last July, hundreds have been killed and predominantly Kurdish cities are under repeated curfews.
Just as the PKK has resumed attacks on military and police targets largely in the south-east, TAK has stepped up its bombings in other parts of the country, targeting the capital to show it can hit the very heart of the Turkish state, revelling in exposing apparent security lapses.
The TAK (Kurdistan Freedom Hawks) was formed in 2004. It is regarded as the hard-line offshoot of the PKK, rejecting any attempt at ceasefire talks with the Turkish state.
On Wednesday, the group said on its website (in Kurdish) that Sunday’s bombing had been aimed at security forces and had not been intended to kill civilians.
However, it warned that further civilian casualties in its attacks were inevitable.
“On the evening of March 13, a suicide attack was carried out… in the streets of the capital of the fascist Turkish republic. We claim this attack,” the group said.