UN Secretary-General Antonio Guterres, speaking at an African summit on Saturday, called for the immediate respect of the Democratic Republic of Congo's (DRC) "territorial integrity" amid a worsening conflict in the country's east.
The M23 group, backed by Rwanda, seized the provincial capital of Goma last month, and this week took the key airport in South Kivu before marching into the city of Bukavu on Friday.
Guterres stressed the importance of avoiding a regional war and warned that "no military solution" would resolve the crisis.
International pressure on Rwanda has intensified, with the European Union condemning the ongoing violations of DRC's sovereignty and urging action. Meanwhile, French President Emmanuel Macron has called for Rwanda to withdraw M23 forces from Bukavu and establish a ceasefire.
Guterres also highlighted Africa's central role in resolving the conflict, pointing to a late-night meeting of the African Union’s (AU) Peace and Security Council.
Rwandan President Paul Kagame attended the summit, while DRC President Felix Tshisekedi, who was absent, was reportedly focused on monitoring the situation on the ground.
The AU, however, has faced criticism for its response, with many viewing the body’s actions as ineffective in the face of the growing threat.
In Bukavu, gunfire echoed through the streets, and reports of looting emerged, including attacks on food reserves and a World Food Programme warehouse.
The M23 group, meanwhile, has demanded the "immediate withdrawal" of Burundian soldiers and urged Bukavu residents to form vigilance committees for security.
Tshisekedi, speaking at the Munich Security Conference, accused Rwanda of "expansionist ambitions" and urged the international community to blacklist Kigali.
Rwanda, for its part, has denied backing the M23 and claims that extremist Hutu groups in DRC threaten Rwanda's security.
The African Union summit, taking place in Addis Ababa, comes as Africa faces multiple conflicts, including a devastating war in Sudan.
AU leaders also discussed the issue of reparations for colonial abuses, reflecting broader regional challenges.
The summit concluded with the election of Djibouti's Mahmoud Ali Youssouf as the new AU executive commission chairman.