Anti-government protesters attend a demonstration in Wan Chai district, in Hong Kong, China October 6, 2019. REUTERS/Athit Perawongmetha

HONG KONG (Reuters) - Hong Kong police fired tear gas on Sunday as protesters defied an emergency law and marched wearing masks through the Chinese-controlled city, witnesses said.

There was no obvious reason for the tear gas, as the rally at Pacific Place on Hong Kong island seemed peaceful, said one witness.

Tens of thousands of protesters wore face masks in defiance of colonial-era emergency powers that threaten them with a year in prison for hiding their faces.

Hong Kong police were bracing for two major protests, fearing a recurrence of Friday night’s violent protests that saw the Asian financial center virtually shut down the next day.