Four South Korean navy men were killed and 18 wounded in a clash with North Korean patrol boats on Saturday off the west coast of the divided peninsula, South Korea said. One South Korean vessel was sunk in the clash in the Yellow Sea, the defense ministry said. South Korea has been co-hosting the World Cup soccer finals and the South Korean team is due to hold its last match in the southern city of Taegu on Saturday evening. (Read photo caption)

"Four South Korean personnel were killed, 18 were injured and one is missing," South Korean defense ministry official Lieutenant General Lee Sang-hee told a news conference.

"A North Korean patrol ship started shooting at around 10:25 (0125 GMT)...one of our navy vessels sank," he said.

The official said there were 27 navy personnel on the vessel that sank.

Two North Korean patrol ships briefly crossed the disputed maritime border -- the so-called Northern Limit Line -- 40 km (25 miles) west of Yeonpyongdo, an island off the west coast of the Korean peninsula, the ministry said in a statement.

The official said the two North Korean boats had returned to their waters after the clash.

It was the twelfth maritime intrusion by North Korean vessels this year including nine by military boats.

The 20-minute morning firefight occurred in the same area as a June 1999 battle in which dozens of North Korean sailors were killed following nine days of North Korean intrusions. That was the first naval clash since the 1950-53 Korean War.

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South and North Korea have been divided since the 1950-53 Korean War and are still technically at war because the fighting ended in a truce.

The Demilitarized Zone separating the two Koreas is one of the most heavily fortified frontiers in the world.

Hours before the clash, the United States said it had proposed to North Korea that a senior U.S. official visit Pyongyang next month to resume the high-level dialogue broken off at the start of the Bush administration's term.

The United States maintains 37,000 troops in South Korea to deter a repeat of the North Korean invasion that sparked the Korean War. Most of the U.S. forces are dug in near the Demilitarized Zone separating the two Koreas.

PHOTO CAPTION

South Korean patrol boats operate near Taeyonpyong Island, South Korea in this June 13, 1999 file photo. Four South Korean navy personnel were killed and 18 wounded in an exchange of fire with North Korean navy ships near their western sea border on June 29, 2002, the South Korean defense ministry said in a statement. (Yun Suk-Bong/Reuters)