A lawmaker has pointed out that one North Korean submarine was unaccounted for in the West Sea around the time when the South Korean Navy corvette Cheonan sank on March 26. Kim Hak-song, the chairman of the National Assembly's Defense Committee, on Monday said, "Two North Korean Shark-class (325 t) submarines disappeared from our military surveillance between March 23 and 27, but the military authorities have still failed to find out where one of them was on March 26."
Kim was speaking to reporters after receiving a report on the sunken ship from the military.
"It was discovered that two Shark-class submarines left and returned to a North Korean base at Cape Bipagot [in South Hwanghae Province] six times on March 23, three times on March 24, but only once on March 26. But I heard that it's impossible to find out how far the submarines went underwater and what they did," he said. "On March 26, one submarine was found to have exchanged communications with the base at Cape Bipagot from a nearby area but the other was unaccounted for."
The defense minister in an emergency National Assembly session last Friday said two North Korean submarines were unaccounted for around that time.
The military has no evidence that the North Korean submarines infiltrated South Korean waters but believe it is possible that they carried out operations in waters near Baeknyeong Island 50 to 60 km off base, considering that they made only one move on March 26 although they had left and returned to the base several times the previous day.
Kim added the lower side of the Cheonan fell off along the welded seam but the upper side was torn off. "Military officers told me that such destruction is inevitably the result of a torpedo or mine attack."
Military officers told him that the iron plate was 11.8 mm thick when the ship was built and had worn down only 0.2 mm according to a periodic inspection in 2008.
Kim said it is more than 70 percent possible to detect torpedoes about 2 km away at a depth of 30 m, but it's difficult to detect new acoustic torpedoes that slowly chase a naval ship following the sound of the engine. "The military believes that North Korea also possesses such torpedoes," he added.
"As a result of analysis of satellite photos, no semi-submersibles made any movements" around the time of the sinking, he said. "It's difficult for light torpedoes with 50 kg TNT of destructive power carried by semi-submersibles to have torn the Cheonan in two."