Japanese defence forces are said to be on alert amid reports that North Korea could be planning a missile launch.
The Yonhap News Agency reported that North Korea had appeared to move a ballistic missile to its east coast, prompting fears of a possible test.
According to ABC, South Korean officials did not confirm the reports, but said they are "closely monitoring the situation".
Tensions remain high in the region after North Korea conducted its fourth nuclear test in January, followed by a satellite launch.
There have been four failed launches of its Musdan intermediate-range weapon since the start of the year, the most recent at the end of May.
United Nations sanctions ban the country from carrying out ballistic missile tests.
UN Secretary General Ban Ki-moon described the last missile launch as “deeply deplorable”.
The latest alerts comes as the annual Northeast Asia Cooperation Dialogue (NEACD) gets underway.
China, Japan, North and South Korea, Russia and the United States are attending the talks in Bejing, with North Korea’s nuclear programme on the agenda.
