Two members of the Islamic State (IS) group, which has claimed responsibility for carrying out a deadly attack in a Moscow concert hall on Friday, had briefly entered and exited Türkiye to extend their residence permit, local media reported on Tuesday.

Anonymous Turkish security sources informed Hurriyet Daily News that the Tajik assailants had been living in Moscow for a long time and needed to leave the country to extend their residency in Russia.

The Tajiks traveled to Türkiye due to its geographical proximity and the limited options available following the embargoes resulting from the Russia-Ukraine conflict, the Hurriyet Daily News reported.

Saidakrami Rachabalizoda and Shamsidin Fariduni spent a couple of weeks in Istanbul before carrying out the attack in Moscow, which killed at least 139 people, according to the sources.

Fariduni reportedly arrived in Türkiye from Russia by air on Feb. 20 and stayed at a hotel in Istanbul's Fatih district. He then departed from Istanbul Airport to Russia on March 2.

Rachabalizoda arrived in Istanbul on Jan. 5 and stayed at a hotel in the Fatih district for a while before flying back to Moscow on the same flight as Fariduni.

The two attackers checked into different hotels in the city, said the Daily, adding that Fariduni shared pictures from Istanbul on his social media account.

In his testimony to Russian authorities, Fariduni reportedly confessed that he had traveled to Türkiye because his visa had expired.

Both individuals were able to travel between Türkiye and Russia using their passports since there was no arrest warrant against them, according to the sources.

Security sources indicated that the two assailants were radicalized in Russia, as their brief time spent in Türkiye was deemed insufficient for radicalization within the country, according to the report.

On Friday night, gunmen opened fire indiscriminately at concertgoers at Crocus City Hall in suburban Moscow. A large blaze later led to the collapse of the building's roof.

The IS group claimed responsibility for the attack on Saturday, saying that the attack was "carried out by four IS fighters armed with machine guns, a pistol, knives, and firebombs."

Türkiye condemned the attack and expressed condolences to the Russian people and government.

The Turkish government designated the IS as a terrorist organization in 2013 and blamed it for a spate of deadly attacks in the country since 2015.

Türkiye has stepped up operations against IS terrorists after the group attacked an Istanbul church in late January, killing a civilian during Sunday mass.