North Korea has confirmed it seized a South Korean fishing boat more than a week ago for crossing into its exclusive economic zone.

North Korean media said Thursday officials are investigating the incident.  The report said the Daeseung 55 was carrying four South Korean and three Chinese crew members.

South Korea last week sent a message to Pyongyang calling for the prompt release of the boat and the seven fishermen, based on international laws and customs, and on humanitarian grounds.

South Korean officials say the fishing boat was captured August 8 off the peninsula's eastern coast.  

Relations between the two Koreas have been tense since the sinking of a South Korean warship, the Cheonan, in March.  South Korea responded by staging naval maneuvers with the United States off its east coast last month and was conducting another exercise off its west coast when the fishing boat was seized.

An international investigation concluded that a North Korean torpedo attack sank the Cheonan on March 26, killing 46 sailors.  Pyongyang denies any connection with the sinking and says the report was fabricated.

Some information for this report was provided by AFP.