South Korean prosecutors on Thursday formally charged a leftist lawmaker with plotting an armed revolt in support of North Korea.

United Progressive Party MP Lee Seok-Ki was charged under the tough National Security Law -- a sweeping piece of legislation enacted in 1948 to guard against espionage and other threats from a belligerent North Korea.

China has banned exports to North Korea of technologies and goods that could be used to make missiles and nuclear, chemical and biological weapons, the government said, as it moves to comply with U.N. resolutions.

Beijing, the North's sole major ally and economic lifeline, has publicly supported sanctions against Pyongyang in the past, though it has come in for criticism from the U.S. and other countries for alleged lax enforcement.

North Korean scientists are able to build crucial equipment for uranium-based nuclear bombs on their own, cutting the need for imports that had been one of the few ways outsiders could monitor the country's secretive atomic work, according to evidence gathered by two American experts.

The experts say material published in North Korean scientific publications and news media shows that Pyongyang is mastering domestic production of essential components for the gas centrifuges needed to make such bombs. The development further complicates long-stalled efforts to stop a nuclear bomb program that Pyongyang has vowed to expand, despite international condemnation.

New satellite images suggest North Korea tested a long-range rocket engine last month, a U.S. research institute said Monday.

While the exact engine type could not be identified, possibilities included the second stage of the Unha-3 Space Launch Vehicle or the second or third stage engine of a much larger rocket under development, the U.S.-Korea Institute at Johns Hopkins University posted on its 38 North website.

South Korea on Monday urged North Korea to review its decision to postpone a reunion for families separated by the Korean War, saying it had "deeply wounded" those chosen to participate.

Hundreds of divided family members from both Koreas were scheduled to meet at the North's Mount Kumgang resort from Wednesday in the first such reunion for three years.

North Korea on Saturday said it would indefinitely postpone highly-anticipated reunions of separated families that were due in four days' time.

The North's Korean Central News Agency (KCNA) cited the government as saying Seoul's "hostile" policy was to blame, though observers believe the move is designed to place pressure on the South to resume cross-border tours to a scenic resort that is an important source of revenue for Pyongyang.

North Korea's chief nuclear envoy appealed for long-stalled talks on its atomic program to resume "without preconditions" on Thursday, Korean media said, days after reports it may have restarted a reactor.

The comments in Beijing by Pyongyang's First Vice Foreign Minister Kim Kye-Gwan were the North's following suggestions -- based on satellite imagery -- that the main plutonium reactor at its aging Yongbyon nuclear facility may be back up and running.

A U.N.-mandated investigator on Tuesday spotlighted "unspeakable atrocities" inflicted on political camp prisoners in North Korea, citing testimony from survivors who saw babies drowned or had to survive by eating lizards.

Retired Australian judge Michael Kirby challenged the secretive Stalinist country to come clean about its record, telling the U.N. Human Rights Council he aimed to draw up a list of violators within North Korea's regime.

U.S. Secretary of State John Kerry will welcome his Chinese counterpart Wang Yi Thursday, when the two are expected to talk about Syria and North Korea over a working lunch.

According to State Department spokeswoman Marie Harf, the long-scheduled meeting will touch on swiftly evolving current events.

South Korean troops shot dead a man trying to swim across a border river into North Korea on Monday after he ignored repeated warnings to turn back, the Defense Ministry said.

A ministry spokesman said he was carrying a South Korean passport that identified him as Nam Yong-Ho, 47.