Hong Kong was plunged into chaos again on Thursday as protesters rallied outside the justice secretary's offices, blocking roads and forcing workers to leave in the latest unrest to rock the city over an extradition bill that has now been suspended.

Millions have thronged the streets in the past three weeks to demand that the bill, which would allow criminal suspects to be sent to the mainland for trial in courts controlled by the Chinese Communist Party, be scrapped altogether.

"I think this movement is very successful because this time the goal is very clear," said one protester, Ken Yau, drawing a contrast with Hong Kong's 2014 democracy movement that gridlocked parts of the Asian financial center for 79 days.