New Delhi, Dec. 7 -- A Russian cosmonaut has been removed from the upcoming NASA and SpaceX Crew-12 mission to the International Space Station, prompting speculation about the reasons behind the sudden replacement.

Roscosmos, Russia's state space agency, confirmed on December 2 that veteran cosmonaut Oleg Artemyev will no longer be flying on Crew-12. He has been replaced by fellow Russian astronaut Andrei Fedyayev. Roscosmos did not provide a specific reason, stating only that Artemyev had been reassigned to another role.

Artemyev's removal is reportedly linked to an alleged national security violation during training in the United States. A report from independent Russian outlet The Insider which cited sources claims Artemyev may have ...