Defense Secretary Ashton Carter arrived in the Republic of Korea on Thursday for a visit dominated by the issue of the Democratic People's Republic of Korea, which fired off two missiles as the Pentagon chief flew to the region.

Carter arrived from Tokyo on the second leg of a trip to the two key US military allies in Asia.

As Carter flew to Japan on Tuesday, the DPRK fired two surface-to-air missiles into the sea off its west coast - a common, attention-grabbing tactic during high profile visits to the region.