North Korea warned South Korea on Monday that any attempt to bring down the communist country would draw "strong measures" from its military, a threat issued even as Pyongyang embarked on a flurry of diplomacy with Seoul, Washington and Beijing.

Armed with a "world-level ultra-modern striking force" that has not yet been publicly revealed, North Korea's Ministry of People's Security and the Ministry of State Security said in a joint statement that the state was poised to mobilize troops to defend itself.

North Korea will take "all-out strong measures to foil the treacherous, anti-reunification and anti-peace moves of the riff-raffs to bring down the dignified socialist system ... and destabilize it," said the statement carried by the Korean Central News Agency.

The warning came as a senior Chinese envoy met with North Korean officials in Pyongyang as part of international efforts to persuade North Korea to return to stalled nuclear disarmament talks.

Wang Jiarui, a top Communist Party official from Beijing, held talks Monday with North Korea's Choe Thae Bok, a senior Workers' Party official, China's Xinhua News Agency said in a dispatch from Pyongyang. Wang told Choe that the longtime ally is ready to work with North Korea to boost bilateral ties, according to Xinhua.

There was no mention of the nuclear issue in the Xinhua report.

Wang likely will meet with North Korean leader Kim Jong Il later Monday to discuss the stalled six-party nuclear talks, the South Korean cable network YTN said on Monday, without citing its source.

Wang is expected to bring Kim a message from Chinese President Hu Jintao, South Korea's Chosun Ilbo newspaper said in a similar report. Pyongyang is expected to promise to make progress in denuclearization in return for Chinese economic aid, the report said, citing an unidentified senior South Korean official.

UN political chief B Lynn Pascoe also was due in Pyongyang on Tuesday.

North Korea walked away from the disarmament talks last year in anger over international condemnation of a long-range rocket launch.

The country later conducted a nuclear test, test-launched a series of ballistic missiles and restarted its plutonium-producing facility, inviting widespread condemnation and tighter UN sanctions.

North Korea wants sanctions eased, better relations with the United States and a peace treaty to formally end the 1950-1953 Korean War.

Also Monday, officials from the two Koreas met in the North Korean border town of Kaesong to discuss restarting joint tours suspended in 2008 when relations were tense.