M23 rebels seized the strategic border town of Uvira in eastern Democratic Republic of Congo, an advance that U.S. officials say was backed by Rwanda and that has killed more than 400 civilians while displacing about 200,000 people.The offensive shattered a U.S.-mediated ceasefire between Felix Tshisekedi and Paul Kagame hailed as historic by Donald Trump, prompted U.S. lawmakers such as Mike Waltz to warn of a wider regional war, and elicited condemnation from Human Rights Watch and U.N. partners describing one of the world’s most serious humanitarian crises.Therese Kayikwamba Wagner urged the U.N. Security Council to consider sanctions while U.S. voices including Marco Rubio said Rwanda violated the Washington Accords, local witnesses such as Maria Esther and Joli Bulambo described life under M23 patrols, and rebel deputy coordinator Bertrand Bisimwa defended operations as Olivier Nduhungirehe denied direct backing.