SEOUL - MOST Chinese fishing boats have suddenly disappeared from the disputed inter-Korean maritime border where South Korea's navy is on high alert for any North Korean provocation, a report said on Thursday.

About 70 of some 90 Chinese fishing boats withdrew overnight from areas near the Yellow Sea frontier, Yonhap news agency said.

The area was the scene of bloody naval clashes in 1999 and 2002.

'Their disappearance makes us nervous as that was exactly what happened before the 2002 clash,' Yonhap quoted an unidentified resident of Yeonpyeong Island near the borderline as saying.

North Korea conducted a nuclear test on May 25 and followed up by renouncing the truce which ended the 1950-1953 war.

It said it 'will not guarantee the legal status' of five South Korean islands including Yeonpyeong, and threatened possible attacks on the South.

The number of Chinese fishing boats in the area had already declined amid growing tensions.

South Korea said on Tuesday it has deployed its most sophisticated high-speed patrol boat armed with ship-to-ship missiles to the area. -- AFP