Hwang Jang-yop, chief architect of North Korea's guiding "juche" philosophy of self-reliance, was one of North Korea's most powerful officials when he fled the impoverished nation 13 years ago in a defection that reportedly enraged Kim Jong Il.
This week, two North Korean army majors were arrested on suspicion of plotting to kill the 87-year-old Hwang, the Seoul Central District Prosecutors' Office said Wednesday.
The two, both 36, confessed to investigators that they were ordered to report back on Hwang's activities and to prepare to "slit the betrayer's throat," a senior prosecutor said. He spoke on condition of anonymity because he wasn't authorized to speak to the media.
The arrests Tuesday come as tensions are escalating over the sinking of a South Korean warship that mysteriously exploded and sank last month near the North Korean border. Speculation is mounting that Pyongyang may have been behind the blast.
Hwang, who lives with around-the-clock police protection due to concerns about North Korean attempts on his life, shrugged off the arrests and said they did not intimidate him, the Yonhap news agency said, citing an unidentified acquaintance.
"I called Hwang after watching news of the agents' arrest but he told me, 'Why are you concerned about such a thing?"' the report quoted the friend as saying.
The North Koreans are the first arrests in connection with a plot against the man who once was a close confidant to Kim Jong Il, the prosecutor said. Hwang worked as Kim's private tutor on his "juche" philosophy, according to South Korean media reports.
The men, identified as Kim Myong Ho and Dong Myong Kwan, made their way from Yanji, China, to Thailand posing as defectors. Thai authorities deported one to South Korea in January, the other in February, the prosecutor said.
The two were arrested after their mission emerged during questioning about their motives for defecting, he said.
One of the suspects attempted suicide during questioning but wasn't seriously hurt, prosecution spokesman Oh Se-in said. Oh gave no further details.
A spokesman at the National Intelligence Service confirmed the arrests but didn't provide additional details. He spoke on condition of anonymity, citing office policy.
They could face the death penalty if convicted of violating the National Security Law.
North and South Korea have remained locked in a state of war since their 1950-53 conflict ended in a truce but not a peace treaty.
Since then, North Korea has waged a number of attacks against South Korea, often relying on a network of spies.
In 1968, 31 North Korean commandos infiltrated Seoul and tried to storm South Korea's presidential Blue House but failed to assassinate President Park Chung-hee. His wife was shot to death in a second assassination attempt on Park's life in 1974.
In 1969, a spy hijacked a South Korean airliner and took dozens of people hostage. The bombing of an airliner in 1987 killed 115 people on board, and a female North Korean spy confessed to the plot. In 1983, North Korean agents masterminded a bombing when then-South Korean President Chun Doo-hwan was visiting Burma. Chun was unhurt but 21 others were killed.
High-profile defectors are also key targets. In 1997, a nephew of one of Kim Jong Il's former wives was killed outside a Seoul apartment, 15 years after defecting to the South. Officials never caught the assailants but believe they were North Korean agents.
Kim Jong Il reportedly has vowed payback for Hwang's defection.
Hwang, a former secretary of the North's ruling Workers Party, has written books and delivered lectures condemning Kim's totalitarian regime.
Speaking to journalists and academics in Washington late last month, he said he made the decision to flee the North after Kim's policies led to mass starvation in the mid-1990s. He said he has no regrets about his decision.
"Everybody other than (leader) Kim Jong Il in North Korea are slaves, serfs," Hwang said through an interpreter at the time. He says change can come only through diplomacy and economic means, not military force.
Hwang's criticism is a "burden for Kim Jong Il and annoyed him because Hwang is a man who knows well about him and was a key figure" in the North, said Yoo Ho-yeol, a professor at Korea University. "For Kim Jong Il, it would have been necessary to punish a betrayer like him to send a message to North Korea's elite."
It was Hwang's second trip to the United States. Previous South Korean governments restricted Hwang's trips over concerns that his criticism of North Korea could complicate efforts to reconcile with Pyongyang, and for fears he would be a target for assassination.
South Korea's current government lifted the ban, calling it a human rights violation.