A protester throws an egg at the police headquarters during a demonstrations in Hong Kong, China, on Friday, June 21, 2019. Hong Kong protesters, including student groups, resumed demonstrations in the city center Friday to demand Chief Executive Carrie Lam step down. Photographer: Eduardo Leal/Bloomberg via Getty Images

Hong Kong police on Saturday condemned protesters that surrounded its headquarters — calling them "illegal, irrational and unreasonable" — as tensions over the city's relations with mainland China boil over into anger toward police forces.

Mostly black-clad young people, who appeared to number in the thousands at their peak, gathered outside the building Friday morning and protested into the early hours Saturday. Some were throwing eggs and writing slogans on the walls of the police headquarters building before eventually dispersing.

Demonstrators are demanding the withdrawal of a proposed Hong Kong government bill that would allow criminal extraditions to mainland China. The Asian financial center has been shaken by two weeks of political and social turmoil, as hundreds of thousands took to the streets in opposition to the proposed extradition bill.

In a strongly worded statement, police said they showed "the greatest tolerance" to protesters outside the headquarters.

"But their means of expressing views have become illegal, irrational and unreasonable," the statement said, accusing demonstrators of disrupting police work. "Police will stringently follow up on these illegal activities."

Protesters are increasingly venting their anger at police after riot squads sprayed tear gas and fired rubber bullets at crowds on June 12 — actions the police commissioner has described as justified but that demonstrators say was excessive. Demonstrators at the police building demanded the release of people arrested over the June 12 protest.