The biggest flashpoint was in Hlaing Tharyar, a poor, industrial suburb of Yangon, Myanmar’s largest city. At least 22 people were killed there, as several garment factories financed by Chinese owners were vandalized and set on fire. It couldn’t immediately be determined who started the fires.

China’s embassy in Myanmar said on Sunday that many Chinese employees were trapped inside and injured as the factories burned. It called on protesters to express their concerns lawfully and urged authorities to punish those responsible.

Nationwide protests continue despite an increasingly violent response from the country’s military authorities. At least 126 people have been killed since the coup, the Assistance Association for Political Prisoners said, as security forces have used lethal force including live fire to break up demonstrations.

The burning of factories marks the first time foreign businesses have been directly caught up in the violence. Some opponents of the coup view China as supportive of the military and have criticized Beijing for refusing to condemn the military takeover and violence against protesters.

Write to Feliz Solomon at feliz.solomon@wsj.com