The eastern African nation is struggling to emerge from a six-year civil war that claimed some 380,000 lives and officially ended with the creation of a government of national unity in February.

Violence has soared in recent months between rival communities, often over cattle raiding which leads to cycles of brutal revenge killings.

In the report, the experts call on the Security Council, which is due to consider enforcement provisions against South Sudan in December, to "take measures to improve the implementation."

They say Uganda was guilty of a "violation" of the embargo when the Ugandan People's Defence Forces (UPDF) entered South Sudan's territory this year, including on October 27.

"A resupply of weapons and ammunition to government security forces or non-state armed groups... would further threaten civilians and risk the peace and security of South Sudan," the experts say in their report.

They also noted that the signatories to the 2018 peace agreement have not honored their commitments to implement it.

In a statement Monday, the NGO Amnesty International called for the arms embargo to be maintained after the "surge in violence against civilians in 2020."

The implementation of the 2018 agreement "has mostly stalled" and the government has less and less financial means to implement it, UN experts said.

They report again that "weapons have been illicitly diverted from government stockpiles to supply militias and other non-state armed groups."

The experts also call for the imposition of "targeted sanctions" on military leaders who have obstructed peacekeeping and diplomatic missions, as well as the delivery and distribution of aid.