Korolev managed to get to the capital of Vilnius where he was detained by the Lithuanian Border Guard at the city's bus station on Aug. 10.
The officer had served in the military unit 59313-39, the joint strategic command of the Eastern Military District of Khabarovsk Krai in Russia's Far East. The unit is stationed in the village of Teysin.
The detained officer was returned to a border checkpoint, from where he reached out to BBC Russian special correspondent Ilya Barabanov.
"I decided to leave Russia on Aug. 3 as I didn't want to participate in the bloody war unleashed by my country. Now I am in Lithuania where I asked for political asylum," Korolev said.
He did participate in the war, but stayed in Russia and has never been to Ukraine, he said.
"We provided the Russian army with ammunition. We collected ammunition from all over Russia, from all units, and all arsenals, and then distributed them to brigades directly in Ukraine," the officer said about his participation in the full-scale war against Ukraine.
Lithuania's Migration Department has yet to respond to BBC's request for comments.