HONG KONG (AP) — Tens of thousands of Hong Kong protesters have kicked off a march from a public park to call for an independent investigation into police tactics.

Marching under sweltering heat, protesters dressed in black walked Sunday behind a large banner reading "Independent Inquiry for Rule of Law."

Massive pro-democracy protests began last month in opposition to a contentious extradition bill that would have allowed Hong Kong residents to stand trial in mainland China, where critics say their rights would be compromised.

The city's leader has declared the bill dead, but some protesters are also calling for her to resign amid growing concerns about the steady erosion of civil rights in the Chinese territory.

The demonstrations have since ballooned into calls for democratic reforms and an investigation into alleged police brutality.