A North Korean merchant vessel crossed the de facto maritime border into South Korean waters in the Yellow Sea on Wednesday and was headed northward and expected to fully cross the de facto maritime border into the north around midnight, Seoul’s military said.

According to the Joint Chiefs of Staff, the military detected an unidentified ship that crossed the Northern Limit Line and entered South Korean waters on the northwestern side of Baengnyeong Island at 6:40 a.m.

At around 12:30 p.m., the military identified the ship as a civilian merchant vessel, as it moved south of Socheong Island. At this point, the South Korean military issued a warning and fired warning shots.

As of 6 p.m. on Wednesday, the military was conducting operations to guide the vessel out of South Korean waters, the JCS said.

“The military is currently taking measures to make sure the North Korean merchant vessel leaves our seas soon,” the JCS said.

The North Korean vessel appears to have accidentally crossed the NLL due to an engine malfunction and bad weather conditions, said a JCS official, adding that it did not show hostility.

The ship was sailing back to North Korean waters by itself at a “very slow speed,” and was expected to fully leave South Korean territorial sea at around midnight Wednesday, the official said.

By Jo He-rim (herim@heraldcorp.com)