A leading human rights group wants Hong Kong officials to “immediately investigate” charges that police used excessive force against journalists and human rights monitors during a massive July 1 protest.

New York-based Human Rights Watch says that a human rights monitor was arrested while videotaping police officers removing protesters who were blocking traffic. It also said the Hong Kong Journalists Association has complained that police used pepper spray against at least 19 reporters, in three cases spraying it directly into their faces.

The report issued Monday says the incidents occurred after the end of the main rally, in which tens of thousands of people marched peacefully to protest government policies and soaring property prices. Some of the marchers converged after midnight in the city's central business district, leading to at least 200 arrests.

Human Rights Watch said it is essential for Hong Kong to demonstrate a commitment to the freedoms of speech and assembly at a time when those same rights are under assault in the rest of China.

The former British colony is guaranteed certain rights under the agreement by which it became a special administrative region of China on July 1, 1997. The July 1 protests have become an annual event, but this year's march was the largest since 2004.