US Secretary of State John Kerry has raised his concerns with Turkish Foreign Minister Mevlut Cavusoglu over the rhetoric that Washington was involved in the assassination of Russian Ambassador Andrey Karlov, State Department spokesperson John Kirby told reporters on Tuesday.

WASHINGTON (Sputnik) — Kirby noted that the allegations by Cavusoglu rest on the fact that the United States shelters exhiled Turkish cleric Fetullah Gulen.

"It’s a ludicrous claim, absolutely false. There is no basis of truth in it whatsoever, and Secretary made this very clear in his discussions today with the Foreign Minister," Kirby added.

A diplomatic source told RIA Novosti earlier in the day that Cavusoglu told Kerry in a phone conversation Tuesday that the so-called Fethullah Gulen Terrorist Organization (FETO), accused by Ankara of organizing a failed coup, was responsible for the assassination of the Russian ambassador

Karlov was killed on Monday by a gunman identified as Mevlut Mert Altintas, a Turkish police officer, who was standing behind the diplomat during a photo exhibition opening in Ankara. The gunman was killed at the scene by the police. The Russian Foreign Ministry said it considered the attack a terrorist act.

Following Monday's attack, chief adviser to Turkish President Recep Tayyip Erdogan and columnist Ilnur Cevik told Sputnik that the killer of the Russian ambassador had been affiliated with the Gulen movement.

On July 15, a military coup attempt took place in Turkey. Ankara accused Islamic preacher Fethullah Gulen, who has been living in the US state of Pennsylvania since 1999, and his followers of playing a key role in the coup. Since July, Turkey has arrested hundreds of military personnel, activists and journalists on suspicion of links with Gulen.