N. Korean boat entered our territorial waters: South

A North Korean navy patrol boat has allegedly crossed into the South's territorial waters amid growing fears of a military confrontation between the two Koreas.

The South Korean Joint Chiefs of Staff said Thursday that a boat had crossed the Yellow Sea border which was the scene of bloody clashes in 1999 and 2002.

The boat stayed almost one hour in the South's waters and reportedly retreated to its own side after three warnings from the South Korean side.

This is while the South has deployed high-speed patrol boats armed with missiles near the disputed sea border with the North.

The boat was said to have been chasing Chinese boats that were operating illegally in the rich crab-fishing zone.

However, a South Korean spokesman said Seoul did not rule out the possibility that the act of intrusion had been pre-planned with the aim of further raising tensions in the peninsula.

Last week, Pyongyang staged its second nuclear test and fired a number of short-range missiles, drawing global condemnation and resulting in a UN Security Council debate over the imposition of additional sanctions against the country.

North Korea, however, seems determined to proceed with the test-fires as it has declared a "no-sail" zone off its west coast and has banned ships from entering the area until the end of next month.

South Korean and American troops in the volatile peninsula have been on high alert since May 25 when the North conducted a nuclear test and launched several short-range missiles.

Pyongyang has accused US President Barack Obama of pursuing the same policies of his predecessor.

North Korea has renounced the armistice that ended the Korean War in 1953 and warned that it will launch strikes on the South in the event that its ships are inspected by international forces looking for nuclear material.