By Sam Kim
SEOUL, June 1 (Yonhap) -- North Korea has intensified landing exercises using amphibious vessels along its west coast, amid growing fears in Seoul that the communist country may be plotting an attack on a South Korean island, a source said Monday.
North Korea, which defied warnings and went ahead with its second nuclear test on May 25, is threatening aggression near its western sea border with South Korea.
The border, known as the Northern Limit Line (NLL), was the scene of naval battles that turned deadly between the Koreas in 1999 and 2002.
North Korea disputes the border, drawn by a U.S. commander at the end of the 1950-53 Korean War, and says it should be pushed south of five nearby South Korean islands, including Yeongpyeong and Baekryeong.
A defense source, speaking strictly on condition of anonymity, said North Korea may be eyeing one of the islands as the target of an armed provocation.
"North Korea has increased exercises using high-speed amphibious boats," the source said, citing intelligence. "We are not ruling out the possibility that North Korea may try to raid one of the islands."
"An attack on Yeonpyeong is likelier because Baekryeong is larger and is guarded by thousands more troops backed by island-wide underground bunkers," he added.
Some 4,000 South Korean marines are stationed on Yeonpyeong, which is located south of a long North Korean coastline from which artillery guns could be fired to wreak havoc on the island.
According to South Korean and U.S. officials, North Korea is also apparently preparing to test-fire a long-range ballistic missile on its west coast.
Another South Korean source said last week that joint training by North Korea's naval and air forces increased at a live-fire shooting range on an island just over 50 kilometers north of the NLL.
Intelligence officials in Seoul said Monday North Korea is prohibiting its vessels from navigating in mid and upper parts of the Yellow Sea.
Denouncing the U.N. Security Council condemnation of its April 5 rocket launch, Pyongyang has vowed to resume its missile and nuclear testing.
North Korea conducted its first nuclear test in October 2006, drawing a U.N. resolution that imposed sanctions on the country.
Pyongyang claims it orbited a satellite with its rocket launch, while the U.S. says nothing entered space, calling the move a test of ballistic missile technology banned under U.N. Resolution 1718.
The two Koreas remain technically at war as the Korean War ended in a truce rather than a peace treaty.
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