The powerful sister of North Korean leader Kim Jong-un on Tuesday warned of a stepped-up action against the arrival of a U.S. aircraft carrier in South Korea, claiming that the U.S. move highlights the North's urgency to bolstering its nuclear forces.

The Carl Vinson Carrier Strike Group arrived in South Korea only days after Pyongyang carried out its fourth missile test this year.

The U.S. aircraft carrier USS Carl Vinson arrived at the southern port city of Busan in South Korea on Sunday as a show of force against North Korea, South Korea's navy said.