HONG KONG  — Hundreds of protesters swarmed into Hong Kong’s legislature Monday night, defacing portraits of lawmakers and spray-painting pro-democracy slogans in the chamber before vacating it as riot police cleared surrounding streets with tear gas and then moved inside.

The three-hour occupation, which ended early Tuesday, came on the 22nd anniversary of the former British colony’s return to China, a city holiday, and reflected mounting frustration with Hong Kong’s leader for not responding to protesters’ demands after several weeks of demonstrations. The protests were sparked by a government attempt to change extradition laws to allow suspects to be sent to China for trial.

Protesters whacked away at thick glass windows until they shattered and then pried open steel security gates. Police initially retreated as the protesters entered, avoiding a confrontation and giving them the run of the building.

Demonstrators stood on lawmakers’ desks and painted over the territory’s emblem on a wall. The crowd also wrote slogans calling for a democratic election of the city’s leader and denouncing the extradition legislation. Many wore yellow and white helmets, face masks and the black T-shirts that have become their uniform.

Police then announced that they would soon move in. A spokesman had earlier broadcast a warning that “appropriate force” would be used. Officers approached shortly after midnight and entered the legislative chambers after protesters had already left. There was no immediate word on any arrests or injuries.