South and North Korean ships exchanged brief but heavy fire Tuesday off their west coast with Seoul claiming "considerable" damage to the North's vessel.

The clashes, coming ahead of U.S. President Barack Obama's scheduled visit to Seoul and other Asian capitals, began after a North Korean patrol boat crossed the demarcation line, South Koran officials told Yonhap news agency.

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

No South Korean casualties were reported.

"It is our initial assessment that the North Korean boat suffered considerable damage," the official said.

South Korean officials said their navy fired warnings shots when the North's patrol boat crossed the Northern Limit Line and the North Koreans fired back. The clashes occurred around 11:30 a.m. near Baekryeong Island, several miles south of the NLL, another official told Yonhap.

"We are analyzing the motive for the North Korean boat's crossing. We do not rule out the possibility that the clash may have been accidental," the official said.

"The battle itself lasted no more than a minute," another official told Yonhap.

The North does not accept the NLL, marked by a U.S. general at the end of the 1950-53 Korean War, the report said. The two Koreas still remain technically in a state of war as their 1950-53 conflict only ended in a truce.

In similar naval exchanges of fire in the past, a North Korean ship was sunk and several vessels from both sides were damaged in 1999, the BBC reported. In 2002, four South Korean sailors and about 30 North Koreans died, the report said.

Relations between the two Koreas had been improving lately despite North Korea's provocative actions, which have included its second nuclear test in May and subsequent missile tests. Those actions resulted in tighter U.N. sanctions, further isolating the Communist country.