SEOUL (AP) — A North Korean fishing boat collided with a South Korea cargo ship early yesterday, leaving two North Koreans missing, an official said.

The 658-ton South Korean ship was carrying sand from North Korea when it collided with the fishing boat in the waters just north of the sea border, Unification Ministry spokesman Kim Ho-nyeon told reporters.

Two of the fishing boat's four crewmen were rescued by the South Korean ship. The other two are still missing, Kim said.

The South Korean vessel was believed to have sailed to a nearby North Korean port for questioning, he said.

Kim said the exact cause of the collision was still under investigation.

He said his ministry received reports about the collision from a related government agency, but Pyongyang had not officially notified the Seoul of the incident.

He said the North was obliged to inform the South of such accidents under an inter-Korean accord.

The collision came amid continuing tensions between the two nations over the shooting death last month of a South Korean tourist vacationing at a North Korean mountain resort.

The North has said the tourist was shot because she entered a restricted military area and ignored warnings to stop. In response, South Korea halted tourist visits to the mountain resort, demanding the North allow investigators into the area.

The two Koreas are still technically in state of war because their 1950-53 Korean War ended with an armistice, not a peace treaty.

Ties between the countries have soured since a pro-US, conservative government took office in February in Seoul with a harder line on the North, prompting the communist side to cut off all official contact.