JUBA, South Sudan (AP) - The main opposition party in South Sudan has reported that its leader, Riek Machar, has been arrested, prompting the United Nations to urge all parties to honor the 2018 peace agreement that ended the country's civil war.

On Monday, the U.N. issued a warning indicating that South Sudan is on the brink of a renewed civil war. This warning follows recent clashes in northern regions, where fighting has erupted between an armed group associated with Machar and government forces. Opposition spokesperson Pal Mai Deng stated in a video address that Machar is currently "in confinement by the government" and that his life is "at risk."

Nicholas Haysom, the head of the U.N. mission in South Sudan, addressed the situation following reports of Machar's detention. He called on all involved parties to "exercise restraint and uphold the Revitalized Peace Agreement." The civil conflict in South Sudan, which lasted five years and resulted in approximately 400,000 deaths, concluded with a peace agreement in 2018 that unified President Salva Kiir and Machar in a coalition government.

Recently, tensions have escalated between Kiir's government and Machar's party. The situation intensified in February when the White Army, a militia loyal to Machar, seized control of an army base in Upper Nile state and attacked a U.N. helicopter. In retaliation, the government launched airstrikes and cautioned civilians in the vicinity of the militia's base to evacuate, stating that they would "face consequences" if they remained.

The airstrikes, which began in mid-March, have already resulted in more than a dozen casualties. Moreover, the U.N. has issued stern warnings regarding the potential emergence of a renewed civil war if the country's leadership does not prioritize national interests. Haysom remarked, "Tonight, the country’s leaders stand on the brink of relapsing into widespread conflict or taking the country forward towards peace, recovery, and democracy in the spirit of the consensus that was reached in 2018 when they signed and committed to implementing a Revitalized Peace Agreement."

Earlier in March, several senior allies of Machar were apprehended by government security forces, a move that supporters of Machar decried as a "grave violation" of the ongoing peace agreement. The political landscape in South Sudan remains precarious, with the potential for violent conflict looming as both sides grapple with escalating hostilities.