South Sudan has claimed the planes were involved in activities that threaten national security

South Sudan's government has grounded four aircraft operated under the UN mission in the East African country, alleging illegal surveillance and the smuggling of natural resources.

Foreign Minister Monday Semaya Kumba said intelligence reports found that two of the aircraft were fitted with advanced surveillance and intelligence systems, which he described as a threat to national security. He said a special committee had been set up to investigate.

The UN mission in South Sudan (UNMISS) has rejected the accusations. Its spokesperson, Priyanka Chowdhury, said UN air operations are conducted transparently and used strictly to support the mission's mandate to protect civilians and support lasting peace in South Sudan. She said UNMISS has been in talks with the authorities "for a while now" to resolve the issue.

It is not the first time the country has moved against UN aviation operations. In 2017, authorities grounded UN aircraft during a dispute linked to peacekeeper deployments at Juba's main airport, arguing the mission had exceeded its mandate.

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UNMISS was deployed in 2011 following South Sudan's independence from Sudan to help protect civilians, support the peace process, and facilitate humanitarian aid delivery.

South Sudan has remained volatile since a five-year civil war that ended with a 2018 peace agreement. Political rivalry, localized violence, and periodic clashes have continued to threaten stability, with the UN warning this year that a deterioration in security could undermine hard-won gains and risk a return to wider conflict if parties do not honor the deal.

More than 9 million people, about 70% of the population in Africa's youngest nation, require humanitarian aid in 2025, including assistance for food, health care, and other essentials, according to UN estimates.