Turkish media reports said on January 14 that two natives of Russia's North Caucasus region of Daghestan have been questioned by police over a suicide bombing in Istanbul last week.
Reports said the Daghestan natives were among six people suspects detained on January 13 in connection with the January 6 bombing in which a female attacker killed one police officer and wounded another.
Three of the suspects were cleared and released after questioning.
Three others, including the Daghestan natives, were accused of "aiding and abetting a terrorist group."
They were released after questioning on January 13 but forbidden to leave Turkey.
Turkish Interior Minister Efkan Ala has said the suicide bomber was identified, but did not release her name.
Some Turkish media reports said she was a Russian citizen from the North Caucasus, Diana Ramazova.
With reporting by Anadolu and Dogan