ISTANBUL -- Turkish security forces have detained 51 suspects in connection with the Istanbul church attack, local media reported on Monday. 23 of the suspects have been handed over to a deportation center for deportation, and 28 suspects are still in police custody, the Demiroren News Agency said. The suspects included Turkish, Tajik, and Russian nationals, it said.

Two assailants attacked the Santa Maria church in the Sariyer district on Istanbul's European side, killing one Turkish citizen during Sunday mass. According to Demiroren, the vehicle used by the suspects in the incident was brought to Turkiye from Poland one year ago, and it had never been used in traffic until last Sunday. Meanwhile, NTV broadcaster aired security camera footage showing the attackers entering the church gate with their masks on. They opened the interior door of the church while the service was going on and checked inside before opening fire.

NTV also noted that Witold Lesniak, consul general of Poland in Istanbul, was attending the service with his family at the time of the attack, and Turkish President Recep Tayyip Erdogan expressed his condolences during a phone call with Lesniak. Turkish Interior Minister Ali Yerlikaya had announced that both attackers, believed to be Islamic State (IS) members, had been arrested in police operations on the same day. Turkiye listed IS as a terrorist group in 2013. The group has claimed responsibility for a number of deadly attacks in the country since then, prompting the Turkish authorities to launch operations against its members.