A U.S. submarine arrived in South Korea today, a few days after the first U.S. nuclear-armed submarine docked in the country in four decades.
 
According to media reports, the USS Annapolis docked at a naval base on South Korea's southern island of Jeju.
 
Earlier, the USS Kentucky had arrived at a port in Busan on the mainland about a week ago.
 
The USS Annapolis, while powered by a nuclear reactor, is not nuclear-armed and is equipped with conventional weapons. Its primary mission is to destroy enemy ships and submarines.
 
According to media reports, the move is seen as a part of joint effort to counter North Korea's nuclear threats.