HONG KONG—Protesters poured into this city’s streets for a second Sunday despite the suspension of a controversial bill to expand the government’s extradition powers, as a week of demonstrations appeared to be spiraling into a broader political movement.

The massive turnout, which organizers estimated at nearly two million, was the third mass demonstration in eight days. It was a rejection of a partial walkback by Hong Kong Chief Executive Carrie Lam, who a day earlier indefinitely suspended work on the bill, which would allow...