China on Friday condemned an incident in which Hong Kong's justice secretary was jostled by masked demonstrators in London, and accused Britain of fuelling pro-democracy unrest.

Hong Kong authorities ordered schools and universities closed Thursday as protesters challenging China's rule brought parts of the city to a near standstill by barricading roads and disrupting public transport links.

Six months of anti-government political action have morphed from peaceful mass rallies into a so-called "blossom everywhere" campaign of violent hit-and-run confrontations with police by groups of black-clad protesters.

Hong Kong pro-democracy protesters clashed with riot police in the city's upmarket business district and on university campuses Tuesday, extending one of the most violent stretches of unrest seen in more than five months of political chaos.

Hong Kong pro-democracy protesters called Friday for city-wide vigils to mourn a student who died from injuries sustained when he fell during clashes with police.

Chinese state-run media on Monday called for a "tougher line" on democracy protesters in Hong Kong, after a weekend of violence following Beijing's plans to tighten control over the semi-autonomous city.

Hong Kong officials apologized to Muslim leaders Monday after riot police sprayed a mosque and bystanders with a water cannon while trying to contain pro-democracy demonstrations in the semi-autonomous Chinese territory.

The city's leader, Chief Executive Carrie Lam, and its police chief visited the Kowloon Mosque to apologize to the chief imam and Muslim community leaders.

Hong Kong's embattled leader abandoned a State of the Union-style speech on Wednesday after she was heckled by rowdy opposition lawmakers during chaotic scenes inside the city's legislature.

Hong Kong's leader invoked colonial-era emergency powers Friday to ban protesters wearing face masks, but the move aimed at quelling months of unrest sparked immediate fresh rallies and vows to defy the new law.

Ripped-up paving stones lay scattered around the graffiti-scarred streets of Hong Kong  after one of the most violent days in a summer of rage, as protesters ready for fresh clashes on Tuesday's 70th anniversary of communist China's founding.

Amnesty International on Friday accused Hong Kong police of using excessive force against pro-democracy protesters, in some cases amounting to torture, criticising a "disturbing pattern of reckless and unlawful tactics".