RIOT police have cleared a Hong Kong pro-democracy protest zone in a dawn raid, taking down barricades, tents and canopies that have blocked key streets for more than two weeks.

Hundreds of officers, some in helmets and shields, descended on the busy district of Mong Kok, a smaller protest zone across the Victoria Harbour from the main occupied area in the city's financial district.

But the key thoroughfare in Admiralty, near the heart of the city's financial district, remained occupied.

The dawn operation was the third in recent days by police to retake streets from protesters. It came hours after Hong Kong chief executive Leung Chun-ying sought to defuse a bitter stand-off with student-led democracy protesters by reviving an offer of talks over democratic reforms in the city.

Police surrounded about 30 protesters who did not put up resistance.