Parts of North Korean landmines apparently churned up by torrential rains have washed up across the border in South Korea, prompting a search by the military for more mines, the defence ministry said.

Two wooden shells of North Korean landmines were found Thursday in a water-harvesting cistern near Hantan River at Cheolwon County, just south of the inter-Korean border, it said.

"They were just empty wooden shells of landmines. They have no explosives and detonators inside. We assume they might have been washed away," a spokesman for the defence ministry told AFP on Saturday.

Soldiers were searching areas near the Hantan and Namdaecheon rivers for other North Korean mines.

They have put up banners and handed out leaflets to warn holidaymakers in the area of the possibility of stray mines and asked them to report anything suspicious to authorities, the spokesman said.

North Korean mines have been carried south by floods and landslides in the past. Last year, dozens of wood-cased mines washed up in the south after heavy rains, killing one South Korean and injuring another.

A landslide triggered by this week's torrential rains also dislodged mines planted decades ago in Mount Umyeon in southern Seoul. Soldiers said they were still looking for about 10 mines there. (AFP)