Turkish police have detained six people, including three foreigners, over last week's suicide bombing in the heart of Istanbul's tourist district, according to local media reports.
Six suspects were in court for questioning by Turkish prosecutors on Tuesday over the deadly attack, the state-run Anatolia news agency reported.
The attack happened a week ago when a female suicide bomber blew herself up in Sultanahmet, the location of most of Istanbul's biggest historic tourist attractions.
A police officer was killed and another injured in the attack.
The nationalities of the foreigners were not immediately available, but Associated Press news agency reported that some Turkish media have said the bomber was a Russian citizen of Chechen origin.
They identified the bomber as Diana Ramazova from the Russian region of Dagestan.
Outlawed far-left Turkish group DHKP-C initially claimed responsibility but then retracted, saying the first statement was an error.
The mother of the suicide bomber - named by the DHKP-C as Elif Sultan Kalsen - was taken to identify the body and said it was not her daughter.
Efkan Ala, Turkey's interior minister, then announced on Thursday that the identity of the bomber had been determined, but declined to give details.
Security has been high in Turkey over the past few months amid fears of attacks by Kurdish fighters and fighters controlling parts of Iraq and Syria up to the Turkish border.