South Korea rejected North Korea's request Monday to send home all three of its citizens who were found adrift last week in a small boat across their sea border, officials said.

The boat with three North Korean men on board was spotted by a South Korean coastguard vessel on Saturday off the South's east coast and the men questioned by security officials, Seoul's unification ministry said.

In a message sent Monday through a cross-border military hotline, the North called for the immediate return of the three men and their boat, the ministry said in a statement.

In response, South Korea offered to send back one man through the border village of Panmunjom this week, saying the two other North Koreans had refused to go home in an apparent bid to defect.

"The two who refused to go back told investigators that they would defect, and our government would respect their wish," a ministry official told AFP.

South Korea has a policy of sending back North Korean fishing boats that stray across the maritime border or those rescued from sea accidents, unless they seek to defect.

Hundreds of North Koreans flee hunger and repression in their isolated communist homeland each year.

Most defectors flee to China and then a third country such as Thailand before coming to the South, but defections across the sea or land border between the two Koreas are rare.