U.S. President Barack Obama has arrived in South Korea for the second leg of a weeklong trip to Asia.
His visit to Seoul comes amid high tensions over North Korea's nuclear program. On April 23, South Korean officials said they believe Pyongyang might conduct a nuclear-weapons test at any moment.
The U.S.-Korea Institute at Johns Hopkins University in the United States announced on April 25 that satellite images taken just two days ago indicate activity at North Korea's nuclear test site that is "probably related to preparations for a detonation."
April 25 is a national holiday -- Korean People's Army Day -- in North Korea, an event usually marked by rallies, concerts, and athletic competitions.
After talks with South Korean President Park Geun-hye, Obama will visit U.S. troops in Korea and then travel on to Malaysia.
On April 25 in Tokyo, Obama and Japanese Prime Minister Shinzo Abe failed to finalize a bilateral trade deal, saying in a statement that gaps remain although there has been progress.
Based on reporting by AFP, dpa, and Reuters