HONG KONG — In the most intense confrontation since the early days of Hong Kong’s pro-democracy protests, hundreds of police officers used pepper spray in the early hours of Wednesday to scatter hundreds of demonstrators who had barricaded a harbor-front road overnight.

The conflict appeared to last less than half an hour, and the two sides settled into an uneasy standoff nearing dawn. But the crackdown, which the police said had included the arrests of 45 protesters, further escalated tensions in this Asian financial center as the authorities showed growing impatience with demonstrations that have choked traffic for more than two weeks.

The swift police action to reopen the road near the offices of Hong Kong’s leader came hours after the Chinese government appeared to ramp up the pressure on Hong Kong’s authorities to act.

In comments carried by the China News Service, an official news agency, the Chinese government made its highest-level denunciation yet of the protesters, accusing them of pursuing a conspiracy to challenge Beijing’s power over the city.