The South Korean military said it fired warning shots to drive off a North Korean patrol boat that had temporarily crossed the disputed western maritime border between the two countries in pursuit of a Chinese fishing boat, The Associated Press reports.

A North Korean patrol boat crossed the "Northern Limit Line" at around 11 am on Saturday, chasing a Chinese vessel in waters off South Korea's Baengnyeongdo Island, but retreated after a South Korean vessel fired warning shots, SK Joint Chiefs of Staff (JCS) said on Sunday.

The intrusion on Saturday came amid the height of tensions in the region over a North Korean weapons display and joint US-South Korea military exercises.

JCS said that the South Korea Armed Forces are closely monitoring North Korean military activities, preparing for various ways of provocation.