The Russian Federal Security Bureau (FSB) claimed it prevented a so-called "terrorist attack" by a Russian anti-Kremlin militia member in Russia's Samara Oblast on March 26.
According to the FSB, the man, a Russian citizen, was a member of the Russian Volunteer Corps (RDK), one of three anti-Kremlin militias that launched raids into Russia from Ukraine in mid-March.
The Kyiv Independent could not independently verify the FSB's claim.
In a press conference last week, representatives of the groups said their goal was to "open a second front" and ease pressure on Ukrainian troops on the Kupiansk axis, with fighters "stabilizing the front" and "easing the pressure of Russian troops in certain areas."
The FSB claimed the man, who it claimed was "operating under the patronage of the Ukrainian special services," had made a bomb and was planning to detonate it at a "humanitarian aid reception point."
The man was allegedly killed by his own bomb while being arrested.
After the deadly terrorist attack on the Crocus City Hall in Moscow last week, the Kremlin has made a concerted effort to tie the atrocity to Ukraine despite Islamic State (IS) taking responsibility and releasing bodycam footage.
During a speech on March 25, Russian President Vladimir Putin said the terrorist attack in the concert hall in a Moscow suburb on March 22 "was committed by radical Islamists," but still alleged that Ukraine was to blame, without providing evidence.
"The U.S., through various channels, is trying to convince everyone that there is supposedly no trace of Kyiv in the bloody terrorist attack at Crocus (concert venue), that it is the banned Islamic State," Putin claimed.
"It is necessary to get answers to a number of questions whether radical Islamists really decided to strike Russia," Putin alleged, insinuating that the attack was carried out on behalf of another "client."
Hours after the attack, Putin attempted to connect the attack to Kyiv, claiming that the detained suspects planned to flee to Ukraine.
The White House said there was no indication that Ukraine was behind the Moscow attack.