The Ankara prosecutor in charge of the case meanwhile released two other suspects and issued an arrest warrant for nine others accused of playing a part in the October 10 attack, the worst of its kind in Turkey's history.
Turkish authorities have said the Islamic State (IS) group is the "number one suspect" for the bombings which targeted a pro-Kurdish and liberal peace rally calling for an end to hostilities between security forces and Kurdish rebels.
Police suspect the bombers were two young Turks from the city of Adiyaman in the south of the country, a stronghold for Islamic militants, according to Turkish media reports.
One has been identified as Yunus Emre Alagoz, brother of the man who carried out a similar attack in July in Suruc, a town in southern Turkey on the border with Syria, that killed 34 people.
The other, identified as Omer Deniz Dundar, had twice been to Syria recently, the reports said.
On Sunday, police arrested around 50 foreign nationals in a sweep targeting suspected IS jihadists with alleged links to the bombings.
Turkey is the main point of entry to Syria for IS recruits.
The attack has raised political tensions to new highs as Turkey prepares for a snap election on November 1, in a country that has become more polarised than ever.
Pressure has piled on President Recep Tayyip Erdogan, with opposition figures blaming him for security lapses over the Ankara attack and failing to crack down on IS.
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Turkish authorities have said the Islamic State (IS) group is the "number one suspect" for the bombings which targeted a pro-Kurdish and liberal peace rally calling for an end to hostilities between security forces and Kurdish rebels.
Police suspect the bombers were two young Turks from the city of Adiyaman in the south of the country, a stronghold for Islamic militants, according to Turkish media reports.
One has been identified as Yunus Emre Alagoz, brother of the man who carried out a similar attack in July in Suruc, a town in southern Turkey on the border with Syria, that killed 34 people.
The other, identified as Omer Deniz Dundar, had twice been to Syria recently, the reports said.
On Sunday, police arrested around 50 foreign nationals in a sweep targeting suspected IS jihadists with alleged links to the bombings.
Turkey is the main point of entry to Syria for IS recruits.
The attack has raised political tensions to new highs as Turkey prepares for a snap election on November 1, in a country that has become more polarised than ever.
Pressure has piled on President Recep Tayyip Erdogan, with opposition figures blaming him for security lapses over the Ankara attack and failing to crack down on IS.
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