Kyrgyzstan ? Mobs of armed men torched Uzbek neighborhoods in Kyrgyzstan on Friday in ethnic clashes that officials said left at least 45 people dead and 637 wounded in a Central Asian nation that hosts U.S. and Russian military bases.

The rioting in Osh, the country’s second-largest city, is the heaviest violence since former President Kurmanbek Bakiyev was toppled in a bloody uprising in April and fled the country. The unrest also spread to the capital, where armed mobs clashed with police and volunteer militia, according to witnesses.

The intensity of the conflict, which pits ethnic Kyrgyz against minority Uzbeks, appeared to take authorities by surprise and threw the fragile interim government’s prospects for survival into doubt.