MOSCOW (AP) — Russia's domestic security agency said Thursday it has captured a Ukrainian security officer who volunteered to spy for Moscow and will send him back because they believe he is a double agent.

The Federal Security Service, or FSB, the main KGB successor agency, said in a statement that the man, Yuri Ivanchenko, was detained on Saturday.

The agency said Thursday that Ivanchenko traveled to Moscow to offer his services to the FSB. It claimed that the CIA had helped the Ukrainian security service prepare Ivanchenko for the mission aimed at eventually exposing his Russian contacts.

The FSB said Ivanchenko, who reportedly solicited his services once before, in 2014, will be sent home and not face any charges.

Russia and Ukraine are locked in a tug-of-war after Moscow's annexation of Ukraine's Crimean Peninsula in 2014 and its support for a separatist insurgency in eastern Ukraine.

In Kiev, chief of the Ukrainian Security Service, or SBU, Vasyl Grytsak confirmed in comments to the Interfax news agency Ivanchenko was an SBU employee but insisted he went to Russia on his own volition. Grytsak said Ivanchenko has had no access to "state secrets" since 2015 and was about to be fired.