Pyongyang presented extensive details but offered no concrete proof.
Then, in April, reports suggested that China's patience with North Korea was wearing thin as Pyongyang continued to conduct nuclear missile tests, and that Beijing was considering a suspension of its crude oil exports to its neighbor should North Korea conduct a sixth nuclear test.
North Korea accused both the U.S. Central Intelligence Agency (CIA) and South Korea's intelligence service of a plan to assassinate its leader with a bio-chemical weapon.
But refusing to crack down on North leads to a North Korea racing toward its nuclear finish-line, USA military build-up in Northeast Asia, and even a direct military conflict with the United States, the expert said. The CIA declined to comment and South Korea has issued no statement so far.
North Korea frequently lambasts the United States and South Korea, but its accusation Friday was unusual in its details.
The spy agencies in June 2014 "ideologically corrupted and bribed" a North Korean citizen who was working in Russian Federation to carry out the alleged assassination on Kim after returning home, the reports quoting the interior ministry.
"Upon his repatriation, the [intelligence agencies] conspired with [the suspect] to carry out a bomb attack on our supreme leader, either during an event at the Kumsusan Palace of the Sun, or at a military parade", the statement read.More news: Rohit, Shami return in India's 15-member squad for Champions Trophy
It said "Kim" had been told that the best method was the use of "biochemical substances including radioactive substance and nano poisonous substance" whose results would "appear after six or 12 months".
North Korea has also repeatedly accused the USA of plotting preemptive nuclear strikes on Pyongyang, practicing dropping nuclear bombs on North Korea with planes which aren't even capable of carrying nuclear devices, and planning a massive invasion of the North.
From alleged South Korean plots to kidnap North Korean waitresses to threats to target the exact coordinates of South Korea's "reptile" anti-North Korea media, the North's propaganda is awash in conspiracy theories and ultraviolent threats.
Such moves would be a step toward the country's goal of developing nuclear-armed missiles capable of reaching the US mainland.
South Korea's military "strongly condemned" the drill and warned of "fatal" consequences if the North provoked it.
The airport attack, blamed by the United States and Seoul on North Korean agents, has been cited by Washington in its efforts to persuade countries to minimize ties with North Korea.
On Thursday, a think tank report from inside the US Congress said that the US' controversial THAAD missile defense system that has begun to be deployed in South Korea may not be capable of actually intercepting North Korean nukes directed around the Korean Peninsula and toward Japan.