Seoul, July 30 (DPA) Seoul Thursday demanded the return of one of its fishing boats which was seized by North Korea after it strayed across the inter-Korean sea border, the South Korean unification ministry said.

The vessel, named 800, with four crew on board crossed several kilometres into North Korean waters when returning from a fishing trip in the East Sea off the Korean peninsula, a ministry spokesman said, quoting the military officials. It was seized around 6.30 a.m. (2130 GMT Wednesday).

'We demand North Korea return the South Korean fishermen and their boat as soon as possible,' Chun Hae Sung said, adding that the demand was passed on to Pyongyang via military channels.

Pyongyang acknowledged the message and said it would look into the matter, the South Korean Yonhap news agency reported, quoting unification ministry officials.