Two individuals from the turbulent Russian Republic of Dagestan were reportedly detained in Turkey in connection with a deadly suicide bombing in Istanbul earlier this month.
On Jan. 6, a female suicide bomber entered a police station in central Istanbul and detonated an explosive device. One officer was killed in the attack, and another was seriously injured.
In total, six people have been detained on suspicion of "aiding and abetting a terrorist group," Turkish news outlet Anadolu reported Tuesday.
Russia's Interfax news agency cited another Turkish publication, Ikhlas, as saying the other four are believed to be from Chechnya.
Russian federal forces have intermittently fought Islamic insurgents in both Dagestan and Chechnya in recent years.
Three of the suspects, including the two of Dagestani origin, were later released from custody, but prohibited from leaving Turkey for the time being, Anadolu reported. Legal proceedings remain ongoing against all six suspects.
The suicide bomber was identified by Turkish police as Diana Ramazova, a Russian national, according to Turkey's Hurriyet news website. Her precise origins remain unknown. Turkish media reports have offered conflicting accounts stating that she was from either Chechnya or Dagestan.
A spokesman for Chechnya's Interior Ministry denied last week that Ramazova was from the republic, saying they had no record of the woman having applied for a passport, the Caucasian Knot website reported.