Sudan on Thursday sharply criticized South Sudan’s call for a U.N. and African Union investigation into alleged atrocities, warning of “appropriate measures” in response to what it called Juba’s continued transgressions and fueling a dangerous escalation in already tense relations.

The diplomatic spat erupted after South Sudan’s Foreign Minister, Ramadan Abdallah, accused the Sudanese army and allied forces of engaging in “terrorism” and killing South Sudanese citizens during a meeting on bolstering African counter-terrorism efforts in New York. He urged the African Union and United Nations to investigate the incidents.

Sudan’s Foreign Ministry swiftly denounced the accusations as “unjustified,” particularly as Khartoum had already announced the formation of its own committee to investigate the events, which allegedly occurred in Al Jazeera state after the Sudanese army seized control of the city of Madani on Jan. 11.

In a strongly worded statement, the Sudanese Foreign Ministry said it had “continued to exercise patience” regarding Juba’s actions, despite the alleged participation of South Sudanese mercenaries alongside the Rapid Support Forces (RSF) militia fighting against the Sudanese army.

Khartoum claimed it had provided evidence of this involvement to South Sudanese authorities, who it accused of failing to curb the recruitment and deployment of mercenaries and of continuing to facilitate the RSF, including transporting and treating its wounded in South Sudanese hospitals.

The statement further alleged that Juba and other South Sudanese cities had witnessed retaliatory violence, including killings, assaults, and looting, targeting Sudanese citizens at the instigation of South Sudanese officials. The Sudanese embassy and its staff were also targeted, the ministry said, in a “clear violation” of the Vienna Convention on Diplomatic Relations.

Sixteen Sudanese citizens, including a doctor, were reportedly killed across four provinces in South Sudan in the violence that followed the allegations against the Sudanese army, sources have confirmed.

The Sudanese Foreign Ministry declared it would take “appropriate measures” to respond to Juba’s actions in international and regional forums and emphasized it would “not hesitate to take the necessary steps to protect its rights and the rights of its citizens.”

The accusations and counter-accusations mark a significant deterioration in relations between the two countries, which have been strained since South Sudan gained independence from Sudan in 2011 following decades of civil war. The conflict in Sudan, which erupted in April 2023, has further complicated the already fragile relationship.