The Chinese military began sending a new group of troops into Hong Kong on Thursday, a move it described as a normal annual rotation of its garrison in the city, but one that was being closely watched because of the ongoing local political turmoil.

The troops were moved as the Hong Kong police denied protesters permission to hold another large march through the city on Saturday, a decision that organisers said they would appeal. One of the protest organisers said he was attacked at a restaurant on Thursday by two men armed with a baseball bat and a cleaver. Hours later, the organiser of another march said he was attacked and beaten by four men.

Chinese state-run media published photos and video of the troop movement, showing trucks, armoured personnel carriers and a ship entering Hong Kong under cover of early-morning darkness.

“This rotation is an annual normal routine action approved by the Central Military Commission,” Lt Col Han You, a spokesman for the Hong Kong garrison of the People’s Liberation Army, said in a written statement. In recent years, the garrison has indeed carried out its rotation at the end of August.

The Chinese military has about 6,000 to 10,000 soldiers in Hong Kong at any given time. The exact number is not made public. The troops have been based here since Hong Kong, a former British colony, returned to Chinese control in 1997.

After the rotation of troops last year, the military said the number of troops and equipment was the same as the previous year. Lt Col Han’s statement this year did not include such a declaration, fueling speculation that the military was expanding its strength in Hong Kong.

The city is in the midst of its biggest political crisis since the handover, with near-daily protests against the government, including some that have turned violent, with demonstrators throwing stones and even firebombs at police. On Sunday, an officer fired a warning shot as a group of protesters with sticks and metal poles charged a group of police officers.