A unit of US special forces tasked with carrying out “decapitation” operations may be aboard a nuclear-powered submarine docked in the South Korean port of Busan, the nation’s newswire reported on Monday, citing a defence source.

The USS Michigan, an 18,000-metric ton submarine, arrived in Busan on Friday, ahead of a ten day joint US-South Korean drill led by the USS Ronald Reagan aircraft carrier.

The US Navy maintains that the Michigan, known for carrying special-ops teams, is docked in a “routine port visit.” The US military also denies training for decapitation missions or regime change, and does not typically comment on Navy SEAL deployments.

However, the presence on board the Michigan of what appeared to be silos for tiny submarines used to transport US Navy SEALs for their most covert missions deep inside enemy territory, has increased speculation that they may take part in training sessions.

The Navy confirmed to Business Insider that the pods, spotted on top of the submarine, are used by Naval Special Warfare units.