North Korea seized a South Korean fishing boat that strayed into the Stalinist country’s territory Thursday after the vessel’s satellite navigation system malfunctioned.

Unification Ministry spokesman Chun Hae Sung told reporters at a briefing today in Seoul that South Korea has demanded that the North return the vessel and its four crew members. North Korea has acknowledged the request and is looking into the incident.

The 29-metric-ton fishing boat crossed into the North’s territory and was seized at 6:17 a.m. local time, Chun. In 2006, North Korea also held a South Korean fishing boat that crossed into its waters for 18 days.

Thursday’s incident will further test the relationship of the two countries that has deteriorated since the communist nation’s May nuclear test. North Korea tested more than a dozen missiles this year, triggering military threats from both sides. South Korea dispatched a high-speed warship to the maritime border last month, bolstering defenses in the event of a naval skirmish.

A South Korean worker is still being detained by North Korea at a jointly run industrial complex on the communist nation’s territory in March for allegedly criticizing Kim Jong Il’s regime.

(via Bloomberg.com)