According to Aivazov, he lost contact with those who recruited him, after which he was forced to fight on the side of the terrorists and was seriously wounded.
He later returned to Europe with a fake Ukrainian passport, but was deported to Russia.
Aivazov is being held in a pre-trial detention center in Makhachkala and charged with terrorism.
Read more in the story of RT correspondent Ilya Petrenko.
* "Islamic State" (IS) - the organization was recognized as terrorist by the decision of the Supreme Court of the Russian Federation of December 29, 2014.