SEOUL - A South Korean navy ship has rescued a North Korean soldier whose boat drifted into southern waters across the Yellow Sea border, officials said Monday.

Security authorities have been questioning the soldier since he was rescued Sunday, a defence ministry spokesman told AFP. The outcome of the investigation would be disclosed later.

The soldier said his boat went adrift while he was fishing and asked investigators to send him back to North Korea, Yonhap news agency reported.

He will be returned later this week through the truce village of Panmunjom in the Demilitarised Zone which bisects the peninsula, it said.

Each side has in the past returned people who crossed the sea border accidentally. But tensions have grown in the Yellow Sea since a brief naval clash there on November 10, the first for several years.

South Korea said it suffered no casualties but set a North Korean patrol boat ablaze. The North's casualties were unknown.

The North refuses to recognise the current sea border and demands it be redrawn further to the south.