Kim Yo Jong is officially the deputy of the body who deals with South Korea relations, but some sources consider her to be a de facto chief of staff to her brother. The ultimatum was reported by state media outlet Korea Central News Agency. Ms Kim said: “By exercising my power authorised by the Supreme Leader, our Party and the state, I gave an instruction to the department in charge of the affairs with (the) enemy to decisively carry out the next action.”
On Thursday, Seoul’s Unification Ministry confirmed it had asked police to investigate two groups, Kuensaem Education Center and Fighters for a Free North Korea for potential violations of the Inter-Korean Exchange and Co-operation Act.
The two groups have said they plan to continue to send leaflets and aids.
North Korean officials have denounced the officials as “mongrel dogs” and “human scum little short of wild animals”.
South Korean authorities have occasionally made moves to prevent such leaflets from being sent.
This includes in 2018 when the leaders of the two countries met at a series of summits.
In 2014, Pyongyang fired machine guns at balloons launched by defector activists.
Seoul has been opposed to the leaflets on the grounds they damage relations, pose risks to people living near the border and cause environmental damage.
On the weekend, some locals stopped efforts to send bottles of rice from the sea.
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“They’re upset that Seoul has done nothing to change the environment and is again telling Seoul to stay out of its nuclear talks with Washington.”
Seoul had predicted the US would lift sanctions in return for the North closing its nuclear reactor site.
The Koreas were once one country.
After being liberated from Japanese control in the Second World War, it was divided into the North, backed by the USSR and China and the South, backed by the US.
The two sides fought the Korean War in the 1950s.
It is estimated three million people lost their lives in the conflict, which ultimately ended in a stalemate.
Last year, South Korean President Moon Jae-in proposed reunification by 2045.
In a speech in Cheonan, he said: “This will probably constitute the most critical juncture in the entire process of achieving denuclearisation and establishing peace on the Korean peninsula.
“Now is the time for both Koreas and the United States to focus on resuming working-level negotiations … at the earliest possible date.”