A Japanese delegation arrived in North Korea on Monday for talks centered on Pyongyang's investigation into the Cold War kidnappings of Japanese citizens, which has marred relations for years.

The four-day visit -- the first official Japanese delegation to the North in a decade -- comes after Tokyo eased sanctions against the secretive state in July when it pledged to revisit the abductions in the 1970s and 1980s by North Korean agents.

The planned resumption of high-level talks between North and South Korea later this week appeared in jeopardy Monday with Pyongyang refusing to confirm its participation.

The two Koreas agreed earlier this month to restart the dialogue, and South Korea had proposed meeting on October 30.

North Korea on Saturday vowed strong action to counter a U.S. attack on its human rights record and issued fresh warnings that the United States was in range of its nuclear weapons.

The threat follows a damning U.N. inquiry into North Korea's human rights record, with the judge who led the investigation urging the world body this week to seek war crimes prosecutions for the regime.

Tensions flared Saturday as South Korean activists attempting to launch propaganda leaflets into the North were thwarted by egg-throwing residents of a border town, following threats of retaliation from Pyongyang.

Hundreds of riot police were deployed as the dispute erupted in the town of Paju, some 40 kilometres (25 miles) north of Seoul, when a dozen people with their faces hooded seized an activists' truck carrying balloons and leaflets.

The commander of U.S. forces in South Korea said Friday that North Korea likely has the ability to produce a nuclear warhead that could be mounted on a missile, but officials later sought to downplay his remarks.

The comments by the commander echoed an internal debate among U.S. spy agencies that came to light last year, in which the military's intelligence service warned the North was closer to achieving a nuclear-tipped missile than previously believed. 

Secretary of State John Kerry said Friday it was too early to discuss cutting the number of U.S. troops stationed in Asia and South Korea, amid increased tensions on the heavily guarded peninsula.

The warning came a day after Washington and Seoul agreed to delay transfer of the Pentagon's control of Korean troops in the event of war with the North. No new date was set to handover the powers.

Kim Jong-Un at least "on the surface" appears to be in control of North Korea, South Korea's Defense Minister Han Min-Koo said Thursday after holding talks with U.S. Defense chief Chuck Hagel.

Han offered a carefully measured assessment when asked whether he believed Kim, who returned to the public eye earlier this month after dropping out of sight for nearly six weeks, was fully in command of the nuclear-armed, totalitarian state.

U.S. and South Korean officials agreed Thursday to delay transfer of the Pentagon's control of Korean troops in the event of war with the North, with no new transfer date set.

Defense Secretary Chuck Hagel said after meeting with South Korean Defense Minister Han Min-Koo that their memorandum of understanding outlined a "conditions-based process" for the transfer instead of relying on a timeline.

North Korea issued fresh warnings Thursday that planned high-level talks with the South might have to be scrapped because of what it called Seoul's arrogant and provocative behavior.

"Inter-Korean ties are now standing at the crossroads," the North Korean delegation that would participate in the proposed dialogue said in a lengthy statement carried by the North's official KCNA news agency.

An American man held for five months in North Korea has arrived back in the United States, U.S. television reported Wednesday, showing his plane landing at an airport in Ohio.

Jeffrey Fowle, 56, whose release was announced Tuesday, arrived at Wright-Patterson Air Force Base, according to the television reports.