Over half a million voters in Hong Kong cast their ballots in primaries held by the city's pro-democracy opposition parties, organizers said on Sunday after polls closed.

The turnout was higher than organizers were expecting, with over 610,000 people casting their ballots digitally and in person.

People stood in long lines outside of 250 polling stations across Hong Kong for the two-day election.

"A high turnout will send a very strong signal to the international community, that we Hong Kongers never give up," Sunny Cheung, a 24-year-old supporter of the pro-democracy opposition, told Reuters.

The vote took place less than two weeks after China instituted a new security law that many fear will erode democracy in the semi-autonomous territory.

"The primary election is our first time to let Beijing know Hong Kongers never bow down to China," said pro-democracy activist Joshua Wong on Saturday before voting began. "We urge the world to put Hong Kong under the global spotlight."

The elections, organized by the Group Power for Democracy, seek to secure a majority of more than 35 seats — more than half of the total number —  for pro-democracy candidates in Hong Kong's Legislative Council election in September.

This would give democracy candidates greater power to veto pro-establishment legislation.

Police raid polling office

Last November, three million people voted in Hong Kong's District Council elections, handing a landslide victory to the pro-democracy camp, who won 17 of the 18 District Councils.

Support stemmed from opposition to a proposed extradition law that would have allowed people arrested in Hong Kong to be sent to mainland China for trial, a bill that has since been withdrawn.

The bill sparked months of violent anti-government protests, which have waned since security forces arrested over 300 people on July 1, the day after the new national security law went into effect.

The district-wide elections, which run through Sunday, were also thrown into question on Friday when Hong Kong police raided the office of a co-organizer responsible for election polling.

Read more: Can free press in Hong Kong survive national security law?

Voting could violate Beijing's law

Many regard the opposition's primary as a litmus test of greater resistance to the security law. Instituted by China last month, the law targets secession, subversion, terrorism and collusion with foreign forces.

Read more: Opinion: China to rule Hong Kong by fear with new national security law

Hong Kongers face uncertainty over what constitutes a violation.

In a government broadcast on Thursday, Secretary for Mainland Constitutional Affairs Erick Tsang said organizers and participants in the primary elections could be in violation of the new law.

He said that polls might be manipulated to interfere with elections in September.

kp, mvb, rs/ng (AFP, dpa,Reuters, AP)