Six Americans caught sending cash, rice to NKorea

South Korean police have detained six US citizens who were attempting to deliver around 1300 plastic bottles filled with rice, dollar notes and Bibles to North Korea, a police official said.

The group had been trying to float the bottles by sea at a border island west of the capital Seoul near the isolated North before being spotted by a military patrol, the official at the Incheon Ganghwa Police Station told Reuters.

The six are suspected of violating the country's disasters and safety act through their actions in an area recently designated as a "risk zone" which prohibits activities deemed harmful to residents, the official said.

"We're investigating them through an interpreter and will decide after 48 hours whether to release them or not," the official said.

Since taking office earlier in June, South Korean President Lee Jae Myung pledged to improve relations with neighbouring North Korea after a spike in tensions between the neighbours.

Lee has suspended anti-North Korea loudspeaker broadcasts on the border and asked activists in the South launching helium balloons carrying leaflets criticising the authoritarian state's leaders to stop in a bid to prevent inflaming ties.

Chung Dong-young, who has been nominated as South Korea's unification minister, said on Wednesday that the leaflet-laden balloons acted as "a catalyst for confrontation and hostilities" between the two Koreas, expressing hopes to rebuild communications with the North.

The activists, often defectors who have fled North Korea and members of Christian groups, also sometimes try to send items such as Bibles and USB sticks loaded with South Korean TV dramas in plastic bottles by sea.

North Korea has described the activists as "human scum" and retaliated last year by launching trash-filled balloons into the South and blaring anti-Seoul broadcasts along the border.

Complaints by residents that the actions of activists put them at risk have led some border areas in South Korea including Ganghwa island to be designated "risk zones" since late last year, enabling authorities to step up monitoring of balloon launches and other anti-North Korea campaigns.