Hong Kong police have arrested more than 500 people holding a sit-in a day after tens of thousands in the former British colony joined a massive march to push for democracy.

Anger at mainland China has never been greater after Beijing warned recently it holds the ultimate authority over the freewheeling capitalist enclave.

That's despite a mini-constitution that gives the city a high degree of autonomy until 2047.

Police said 511 people were arrested Wednesday for unlawful assembly and preventing police from carrying out their duties. They were holding an overnight sit-in after the rally.

Police said 98,600 people joined Tuesday's rally at its peak, while organizers said 510,000 turned out, the highest estimates in a decade. Hong Kong University researchers put the number at between 154,000 and 172,000.