HONG KONG — Christmas Eve, ordinarily a night of revelry in Hong Kong, was filled with tear gas and pepper spray as riot police officers clashed with pro-democracy protesters who gathered at malls and shopping districts.

Two dozen people were injured, including one protester who fell over a railing and at least one floor in a shopping mall while trying to evade arrest, and another who fell from the roof of a restaurant that was being raided by the police.

The police said the man at the mall was being treated for injuries at a hospital and had been arrested on charges of assaulting an officer. Officials did not comment on the other man’s status, but witnesses said he was conscious at the time of his fall.

The protests, which began in June over a since-withdrawn proposal that would allow extraditions to mainland China, have entered a period of relative calm. But occasional flare-ups continue.