Pyongyang on Tuesday released a South Korean detainee "arrested for entering the North illegally" last month, Seoul's unification ministry said, as ties improve between the two countries following a summit between their leaders in April.

"Our side received a South Korean national surnamed Seo, born in 1984, through Panmunjom from the North at 11:00 am (0200 GMT)" on Tuesday, the ministry said in a statement, referring to the truce village in the Demilitarized Zone dividing the two countries.

The release followed a message from Pyongyang on Monday informing Seoul that the North Korean authorities had arrested the South Korean for "entering the North illegally on July 22", the statement added.