The North Korean leader’s powerful sister denounced a stopover by a U.S. nuclear-powered submarine in South Korea as a “frantic” attempt to demonstrate American military strength, claiming that a DPRK spy satellite detected the vessel’s arrival.

In a statement released Tuesday night, Kim Yo Jong asserted that the Aerospace Reconnaissance Agency detected “an abnormal object at a wharf” in the port city of Busan on Monday morning, in an apparent attempt to demonstrate the country’s improved reconnaissance capabilities since putting the satellite in orbit last year.