Asia tour: Obama in Seoul amid nuclear test fears
US President Barack Obama is in Seoul for a visit that comes amid concern that North Korea may be planning a fourth nuclear test, the BBC reported.
Mr Obama, who arrived from Japan on the second stop of his Asian tour, will hold talks with South Korean leader Park Geun-hye.
Their talks are set to focus on North Korea, following reports of activity at the Punggye-ri nuclear test site.
Mr Obama is also expected to express grief over last week's ferry disaster.
More than 300 people were killed or remain missing after the Sewol passenger ferry sank off South Korea, in a tragedy that has shocked the nation.
Most of those who died were teenagers on a school trip.
Mr Obama is expected to hold talks with Ms Park, visit US troops and then fly to Malaysia on Saturday.
Speaking in Japan, he called the North Korean problem "the most destabilising, dangerous situation in all of the Asia-Pacific region", and described China's role in influencing Pyongyang as "critically important."
Earlier this week, South Korea's military said it had detected "a lot of activity" at the North's nuclear test site, suggesting it was either planning a test or would pretend to stage one.