Hong Kong officials apologised to Muslim leaders on Monday after riot police sprayed a mosque and bystanders with a water cannon while trying to contain pro-democracy demonstrations in the semiautonomous Chinese city. The city's leader, Chief Executive Carrie Lam, and its police chief visited the Kowloon Mosque to say sorry to the chief imam and Muslim community leaders. They left without commenting but the mosque leaders told reporters that the officials apologised. "Our mosque is not damaged, nothing is done wrong. Only thing is that they should have not done it. For that they apologised so we accept it," said Saeed Uddin, honorary secretary of the Islamic Community Fund of Hong Kong. During Sunday's protest, a police water cannon lorry that was passing by the mosque suddenly sprayed a stinging blue-dyed liquid at a handful of people standing in front of its gate, according to video of the incident by pro-democracy politician Jeremy Tam. The mosque's front steps, metal gate and pavement outside were stained with the blue liquid while the people caught in the plume were left gagging, coughing and trying to rinse the solution from their eyes, the video shows. Volunteers later arrived to help clean up, and by Monday morning the blue coating was largely gone. Mr Tam said on his Facebook page that he and two others, an Indian businessman and the head of a charity for ethnic minorities, went to the hospital to check for injuries. Local broadcaster RTHK reported the people outside the mosque were there to guard it. Hong Kong authorities scrambled to minimise the fallout from the incident, which protesters seized on as the latest example of what they call unnecessarily harsh police tactics. Police used the water cannon along with tear gas and pepper spray to battle protesters who remained on the streets after the end of an unauthorised rally, vandalising and setting fire to shops with mainland China ties. They were rallying to call for broader political rights and police accountability, in the latest turmoil to grip the financial centre since early June. Hong Kong is home to more than 300,000 Muslims, according to the Islamic Community Fund, which runs the city's five mosques and two Muslim cemeteries. They first arrived in the 19th century after being recruited in India by British colonisers. Police said on Sunday that the spraying was an accident and sent representatives to meet mosque leaders. "It is most unfortunate that the dispersal operation has caused unintended impact on the Kowloon Mosque," the force said on its Facebook page. Later on Monday, organisers planned an evening sit-in at a suburban train station on the three-month anniversary of a violent attack there on protesters by men with suspected organised crime ties. Hong Kong's subway operator said it would close the station by early afternoon in an apparent bid to foil the protesters, who have trashed and torched subway facilities in anger at the operator's support for authorities.