(CNN) -- North and South Korean naval forces exchanged fire Tuesday in disputed waters, South Korea's semi-official Yonhap news agency reported.

The two Koreas clashed off their west coast, the first such incident in seven years, Yonhap reported, citing an unnamed South Korean defense official.

"It wasn't a close-range battle," the Navy official said. "We fired heavily on the North Korean vessel.

"It is our initial assessment that the North Korean boat suffered considerable damage," said the official who declined to be identified because the information was preliminary. "No South Korean casualties were immediately reported."

A senior Obama administration official told CNN that South Korea was downplaying the incident, which doesn't appear to be deliberately provocative.

A patrol ship from the Communist North crossed the demarcation line late Tuesday morning, prompting the South's navy to fire warning shots, the South Korean official told Yonhap.

"The North Koreans then fired back," the official said.

Another defense official told the news agency that South Korea was not ruling out "the possibility that the clash may have been accidental."

North and South Korea have been bitterly divided since the 1950-53 war between them ended without a peace treaty.

There was, however, an armistice with the U.N. Command establishing the Northern Limit Line (NLL), a demarcation on the Yellow Sea designed to avert clashes at sea. But the two nations dispute the exact location of the sea border and North Korea does not observe the line.

Clashes have occurred before in the Yellow Sea, especially during crab fishing season, according to the defense news Web site Globalsecurity.org. Since 2001, North Korean vessels have crossed the NLL 65 times, though most of these incidents do not turn violent.

The first clash since the Korean War that turned deadly occurred in June 1999 when a North Korean ship was sunk. And in 2002, a series of North Korean incursions sparked an exchange that killed four South Korean sailors and wounded nine others.

Nine incursions had been reported this year through September, according to Yonhap.

The naval skirmish comes just days after North Korea pressed for direct talks with the United States, saying the two need to settle their differences before meaningful multilateral nuclear discussions could proceed, state media reported.

The reclusive Communist state pulled out of nuclear talks in April to protest the United Nations' condemnation over its nuclear test and missile launches. The communist nation has accused Washington of violating its sovereignty by singling it out and reporting it to the United Nations Security Council.