A strong earthquake struck near Mandalay, Myanmar’s second-largest city, on Friday, damaging or collapsing bridges and buildings across a swath of Southeast Asia, killing at least 20 people in Myanmar and injuring hundreds of others.

The 7.7-magnitude quake struck just before 1 p.m. local time, and a strong, 6.4-magnitude aftershock followed 11 minutes later. The shaking was felt in southern China and Vietnam and as far away as Bangkok, Thailand’s capital, where a 30-story skyscraper under construction collapsed, killing at least three people.

Details of casualties and damage in Myanmar, which has been ravaged by a four-year-long civil war, were not immediately clear. In Bangkok, people flooded into the streets out of fear of aftershocks, traffic was at a standstill, and videos captured water surging from the rooftop pools of hotels and residential towers.