South Korea’s unification ministry has urged human rights groups to “refrain from” sending anti-regime leaflets to North Korea, while warning Pyongyang that Seoul will respond “strongly” to threats of “retaliation” against ROK citizens.

The statement on Friday comes as a U.S. nongovernmental organization prepares to host an annual series of events on DPRK human rights called North Korea Freedom Week, which a prominent defector-activist has used as an occasion to launch balloons carrying leaflets in the past.