North Korea has announced it would close its border with South Korea from next month, accusing Seoul of taking confrontation "beyond the danger level."

The communist state's military told its South Korean counterpart today that a measure "to strictly restrict and cut off all the overland passages" would take effect from December 1.

A border closure would effectively shut down joint projects such as the Seoul-funded Kaesong industrial complex just north of the frontier.

The announcement follows months of icy relations, including threats by the communist state to expel South Koreans from Kaesong in protest at the spreading of cross-border propaganda leaflets by Seoul activists.

The North's official Korean Central News Agency (KCNA) said the border move was in response to Seoul's failure to honour agreements reached at inter-Korean summits in 2000 and 2007. It said the border restrictions were the "first step" in response.

KCNA said the head of the North's delegation to inter-Korean military talks sent a notice to the South's armed forces today.

"The South Korean puppet authorities' unchanged stand and attitude towards the historic two (summit) declarations have been finally confirmed," KCNA quoted the notice as saying.

"Such stand and attitude are leading to the grave wanton violation of all the North-South agreements made according to the declarations."

Seoul's confrontational moves were "going beyond the danger level," it added.

South Korean officials could not immediately be reached for comment.

Cross-border relations soured after conservative South Korean President Lee Myung-Bak took office in February and promised to take a firmer line with the North after a decade-long "sunshine" engagement policy.

Mr Lee said he would review summit deals reached between the North and his predecessors, which envisage joint economic projects costing tens of billions of dollars.

The North is also angry with South Korean activists who launch balloons carrying hundreds of thousands of leaflets across the heavily fortified border.

These criticise the North's leader Kim Jong-Il as a dictator and repeat claims that he is in poor health - an especially sensitive topic for Pyongyang.

More than 32,000 North Koreans earning $60 a month work for 79 South Korean factories at Kaesong. The project earns the North tens of millions of dollars a year.

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