Beijing has described the storming and trashing of Hong Kong’s legislature on Monday by protesters against an extradition bill as a “blatant challenge” and accused foreign countries of helping to foment the unrest.

Protesters used metal poles and street signs to smash their way into the Legislative Council, the city’s de facto parliament, where they sprayed graffiti and unfurled a colonial era flag, before fleeing a few hours later ahead of a police operation to clear the building.

The protests followed mass demonstrations over the past three weeks against a government bill that would allow the extradition of criminal suspects from the territory to China. The protests have plunged one of Asia’s premier financial centres into its worst political crisis since its handover from the UK to China 22 years ago.