Tensions between South and North Korea have escalated once more after the South Korea fired warning shots at a North Korean patrol boat that briefly moved south of the countries' disputed maritime border in the Yellow Sea, Seoul's defense ministry said on Monday.

A South Korean military official told the Yonhap news agency that the North Korean vessel crossed the Yellow Sea border just before 7 a.m. Sunday, but retreated northward after the warning shots were fired into the water.

"It quickly retreated after the South Korean navy fired warning shots," a ministry official said.

Pyongyang refuses to recognize the de-facto maritime boundary between the two Koreas, the Northern Limit Line, arguing that it was unilaterally drawn by U.S.-led United Nations forces after the 1950-53 Korean War. As a testament to this, North Korea frequently fires artillery shells and moves naval ships near to or across the line, according to DW.

As such, incidents like this are not uncommon and though they don't usually don't amount to anything, limited naval clashes did emerge in 1999, 2002 and 2009 due to such provocations.

However this incident underscores the heightened tensions between the two nations following the North's launch of a long-range rocket on Sunday, reported the AFP. The South argues the launch was a  disguised ballistic missile test and has remained on a high state of alert ever since.

Emphasizing Seoul's current state of mind, South Korean President Park Geun-hye has called for heightened vigilance against any further provocation from North Korea following Sunday's missile launch and last month's nuclear test.