By Na Jeong-ju

A North Korean committee handling South Korea policies tried to send a strongly-worded warning to President Lee Myung-bak through the South's Unification Ministry, but the ministry refused to accept it, a ministry spokesman said Thursday.

It is the latest indication of deteriorating relations and rising tensions between the two Koreas.

Seoul's refusal prompted Pyongyang to disclose the message through its official Korean Central News Agency late Wednesday.

The message repeated Pyongyang's latest demand that Seoul apologize for its alleged provocations, remove all military slogans slandering the North's top leaders and punish those who are responsible.

"The North's Committee for the Peaceful Reunification of Korea tried to deliver the message through an official at the truce village of Panmunjeom, but we rejected it," the spokesman said on condition of anonymity.

"That's because it was not appropriate for the committee to send a message directly to Cheong Wa Dae. When we asked about what the message was about, the committee didn't say."

Pyongyang has also refused to accept South Korea's messages in the past, the official said without elaborating.

The committee said in the message that "If the South continues a smear campaign defiling the dignity of our leadership, we will resolutely counter them with an all-out military retaliation."

In a separate statement Wednesday, the North also threatened to launch a retaliatory "sacred war" against South Korea over the smear campaign.

The threat followed media reports here that army units at the inter-Korean border were using slogans slandering the North's leader Kim Jong-il and his heir apparent Kim Jong-un during training.

A unit wrote on its wall, "Let's hack the Kims into pieces." A banner hung at the entrance of the unit reads, "Let's ram guns and swords into the chests of North Korean puppet solders."

Inter-Korean relations have soured following North Korea's two deadly attacks last year that killed 50 South Koreans. Defying Seoul's demand for an apology and a pledge not to attack the South again, Pyongyang has continued to blast President Lee and his conservative government, threatening military action.