"In this case it is hardly worth hurrying to any conclusions until the investigation determines - as our president said - who was behind the murder of our ambassador," Kremlin spokesman Dmitry Peskov told reporters.
In the first official accusation against Gulen by a top Turkish official over the killing, Turkish Foreign Minister Mevlut Cavusoglu told US counterpart John Kerry in a phone call yesterday that Turkey believed Gulen's group FETO was involved, the foreign ministry said.
President Vladimir Putin will take part in mourning ceremonies for the slain ambassador tomorrow as he is laid to rest in his homeland.
Veteran diplomat Karlov was shot nine times in the back by off-duty Turkish policeman Mevlut Mert Altintas at the art gallery opening of a show of Russian photography on Monday.
His body arrived back in Moscow late Tuesday after Russian investigators landed in Turkey to help probe the assassination.