South Korean officials say they have arrested a North Korean defector on suspicion of plotting to murder a leading anti-Pyongyang activist.
The defector was allegedly armed with poison needles intended for an attack on high-profile activist Park Sang-hak.
Park Sang-hak is another North Korean defector, who leads a campaign that sends leaflets attacking Pyongyang's leaders to the North.
The Associated Press reported that intelligence sources named the arrested man as Ahn, but would not elaborate.
The investigators refrained from immediately linking the latest case to North Korea and would not comment on local media speculation that Ahn might be an infiltrator similar to one jailed earlier this year.
In the previous case, a North Korean agent to 10 years in prison for plotting to assassinate Hwang Jang-yop, a high-profile defector and former senior member of the North's ruling party.
The BBC said Ahn is understood to be a former commando in his 40s who defected to the South in the late 1990s.
Park told Agence France-Presse that Ahn had asked to meet for a meeting on September 3, but intelligence officials warned him not to go.
Ahn told me by phone that he was to be accompanied by a visitor from Japan who wants to help our efforts. But then I was told by the NIS (National Intelligence Service) not to go to the meeting due to the risk of assassination.
Park is the leader of the Fighters for Free North Korea activist group, which flies balloons containing leaflets, DVDs, radios and U.S. dollar bills over the border.
He has come under increasingly intense criticism from Pyongyang, which has threatening to fire retaliatory artillery shells into the South.
If charged under the South's National Security Law, Ahn could face the death penalty.
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