Istanbul anti-terror police this morning detained eight people suspected of links to the New Year gun attack on a nightclub in the Turkish city that left 39 dead, according to the Dogan news agency.
Dogan said police were pressing on with operations after making the first arrests over the attack.
The suspected gunman is still believed to be on the run.
The so-called Islamic State militant group earlier claimed responsibility for the attack.
In a statement circulated on social media, the jihadist group said one of the "soldiers of the caliphate" had carried out the attack on the Reina nightclub, on the bank of the Bosphorus.
The statement said the attacker used hand grenades and a gun in the assault.
It accused Turkey, a majority-Muslim country, of serving Christians, in a possible reference to Turkey's alliance with the international coalition fighting IS in neighbouring Syria and Iraq.
The statement said the attack was in response to Turkey's military intervention against IS in Syria.
Turkey is a backer of Syria's opposition, but has also been waging its own military intervention in Syria since August, targeting both IS and Kurdish fighters.
The US-led coalition carrying out strikes against IS in Syria uses airbases inside Turkey.
A string of deadly attacks rocked Turkey throughout 2016, with some claimed by a Kurdish extremist group and others suspected to be the work of IS.
The Reina nightclub attacker is still at large, with Turkey's interior minister saying intense efforts were under way to find him.
Source: National News Agency