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".

As pro-democracy protests grind on for a fourth month, Hong Kong has been left counting the cost, with the city’s tourist industry battered and businesses forced to lay off staff as they struggle to stay afloat.

A passenger train derailed during the morning rush hour in Hong Kong on Tuesday leaving eight people injured, authorities said.

Images from the scene showed three carriages had left the tracks and were zigzagged across the rails near Hung Hom station in Kowloon -- a busy interchange that provides services to mainland China.

Riot police fanned out across Hong Kong on Saturday and thwarted plans by pro-democracy protesters to target the airport, days after the city's leader made a surprise concession which was rejected by the movement as too little, too late.

Prominent Hong Kong democracy activists were arrested Friday in a dragnet that came as protesters planned to rally this weekend in defiance of a police ban.

Beijing on Tuesday voiced "strong dissatisfaction" with a joint statement issued by the G7 leaders, who backed Hong Kong's autonomy and called for calm after months of civil unrest.