US President Barack Obama is in Seoul for a visit that comes amid concern that North Korea may be planning a fourth nuclear test.

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.

(BBC)