North Korea's military threatened on Tuesday 'strong physical retaliation' against South Korea's planned naval drills near their disputed sea border and warned civilian ships to stay away from the area.

South Korea plans to hold five-day naval drills in the Yellow Sea, including near the border, beginning Thursday in response to the deadly March sinking of a South Korean warship blamed on North Korea.

North Korea vehemently denies involvement in downing the 1,200-ton Cheonan, and has demanded its own investigators be allowed to visit South Korea to examine the results. Seoul has rejected the North's repeated requests.

The North made a decisive resolution to counter the reckless naval firing projected by the group of traitors with strong physical retaliation, the North's military said in a notice carried by Pyongyang?s official Korean Central News Agency.

The North's military also warned all civilian ships to stay away from areas near the sea border.

The North's military denounced South Korea's planned drills as political provocations aimed at keeping the sea border, the scene of deadly skirmishes between the two sides in 1999, 2002 and last year, as it is.

South Korea's Defence Ministry officials were not immediately available for comment.

The western maritime boundary has long been considered a flash point between the two Koreas, because the North does not recognize a line the United Nations unilaterally drew at the end of the 1950-53 Korean War.

Last month, South Korea and the United States held naval drills in the East Sea off the coast of the Korean peninsula to warn the North that further provocations will not be tolerated.

The North had threatened to respond to the joint military exercises with powerful nuclear deterrence, though there was no sign of unusual North Korean military activity during the drills.

Pyongyang routinely accuses the U.S. and South Korea of staging military drills as a rehearsal for an attack on North Korea. Washington and Seoul say the exercises are purely defensive and they have no intention of invading the North.

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