The president of the United States observed violent contests in a blood-spattered ring, chatted with celebrities and, at times, engaged in intense discussions with his Secretary of State, Marco Rubio, and other advisers, in full view of the thousands of attendees.
Rescue teams are searching through the rubble, with up to 15 people believed missing.
Kigali accuses the central African organisation Eccas of pandering to the demands of Kinshasa.
Trump has long been critical of how the Geneva-based institution handled the Covid-19 pandemic.