Pro-democracy protesters camped out on the streets of Hong Kong for more than six weeks face arrest after a court authorised police to help bailiffs clear them from occupation sites, a senior government official has warned.

The acting chief executive, Carrie Lam, also said there was no room for further dialogue with the student-led protesters, whom she said had hardened their position, raising the prospect of more violence as the government struggles to end the mostly peaceful standoff.

Lam’s remarks to reporters came a day after Hong Kong’s high court extended injunctions requiring protesters to leave two of the three protest sites while also authorising bailiffs to seek police assistance to clear the areas.

Lam said “the police will give full assistance, including making arrests where necessary” to enforce the injunctions.

She urged protesters to “voluntarily and peacefully” leave the occupied areas so that roads and building entrances could be reopened.

The demonstrators have been occupying key thoroughfares since 28 September to protest against the Chinese central government’s requirement that candidates for inaugural 2017 elections for Hong Kong’s top leader be screened by a panel of Beijing-friendly elites.

On Monday, a judge extended interim restraining orders taken out three weeks ago by bus, minibus and taxi operators against protesters blocking streets in Hong Kong’s densely populated Mong Kok district. The owner of an office building next to the main protest site surrounding city government headquarters in Admiralty district also had a restraining order extended.

Previous police attempts to clear protesters from occupied areas with force have backfired, drawing more demonstrators on to the streets and forcing authorities to back off.

• This article was amended on 12 November 2014. An earlier version said that Carrie Lam is acting chief secretary rather than acting chief executive.

