SEOUL, South Korea - South Korea denied North Korea's claim it hired an agent to track its leader Kim Jong Il in what the North suggested was an assassination plot.
The North's Ministry of State Security made the claims late Thursday, saying it recently arrested an agent it alleged was trained by the South to gather information about Kim's movements.
The sensational allegation came amid a serious worsening of relations between the divided Koreas, as well as intense speculation about Kim's health since he was reported to have had a stroke and brain surgery in August.
"The (South's) organization sent him speech and acoustic sensing and pursuit devices for tracking the movement of the top leader and even violent poison in the end," the North Korean ministry said in a statement, carried by the Korean Central News Agency.
It said the "terrorist mission" was ordered by a South Korean intelligence organization "to do harm to the top leader."
South Korea's National Intelligence Service flatly denied the North's accusations.
"This has nothing to do with us," said an agency official on condition of anonymity, citing department policy.
He said the comment represents South Korea's official position on the issue.
The North's statement did not mention Kim Jong Il by name but South Korean Unification Ministry spokesman Kim Ho-nyeon said the North's state media has used such wording before in reference to him.
Kim of the Unification Ministry, which handles relations with the North, said he was in no position to confirm the report.
Tensions on the Korean peninsula have run high since the pro-U.S., conservative government of President Lee Myung-bak took office in Seoul in February with a pledge to take a tough line on the North.
Ties worsened earlier this month after the North restricted traffic at the countries' border, expelled some South Koreans from a joint industrial zone and suspended a tour program to the ancient North Korean city Kaesong.
The North's statement also said authorities recently arrested unspecified agents who tried to gather soil, water, leaves and dust in the country's major munitions industrial area to gather information on its nuclear program.
Earlier this month, international talks on the North's nuclear development ended in a stalemate over its refusal to put into writing any commitments on inspecting its past atomic activities.
Though it was impossible to verify the North's espionage claims, the divided states -- which fought the 1950-53 Korean War -- are known to actively spy on each other and have carried out plots to assassinate each other's leaders in the past.
South Korean experts said it was rare for North Korea to issue a statement on an alleged assassination attempt and were divided over the claim's authenticity.
Yoo Ho-yeol, an expert on the North at Korea University, said it appeared to be aimed at justifying the North's recent rhetoric and actions against the South, adding it was highly unlikely Seoul would have carried out such a plot.
Koh Yu-hwan, a professor at Dongguk University, also thought the South was likely not behind a plot.
"I think such an attempt was made though I'm not sure whether that was committed by the South," he said.
South Korea trained a group of ex-convicts to kill Kim Il Sung -- Kim Jong Il's father and North Korea's founder. But in 1971 the plot was aborted and the commando forces killed their trainers, fought their way into Seoul and blew themselves up.
South Korean security forces in 1968 repelled an attack by North Korean commando troops near the residence of then-South Korean president Park Chung-hee.
North Korea has denied the 66-year-old Kim was ever ill, recently churning out reports and photographs depicting him as healthy and active. KCNA reported Thursday that Kim inspected a machine plant -- the latest dispatch on his public appearances. The report, however, did not say when he made the visit.
