Aung San Suu Kyi, the civilian leader of Myanmar, and several members of her party have been detained by the military, which has declared a state of emergency. Internet and cellphone network outages have also been reported. Late Sunday night, White House press secretary Jen Psaki said the U.S. was “alarmed by reports that the Burmese military has taken steps to undermine the country’s democratic transition and... opposes any attempt to alter the outcome of recent elections.” Psaki warned that the U.S. “will take action against those responsible if these steps are not reversed.”

A Nobel Peace Prize winner, Aung San Suu Kyi had received international condemnation in recent years for her support of the military after denying that it had carried out genocide against the county’s Rohingya Muslims, a minority group. While Aung San Suu Kyi’s party won the November election—in which the country’s elections commission has stated there was no significant voter fraud—the military has disputed its results. Myanmar was run by a military junta from 1962 to 2011.