Hong Kong pro-democracy lawmakers were arrested and then released on Monday over their involvement in mass protests for free elections, the latest step in a widespread investigation that has been accused of seeking to intimidate activists.
Police have vowed to investigate the "principal instigators" of the street blockades that ended in December when rally camps were cleared.
Albert Ho and Helena Wong, both of the Democratic Party, voluntarily turned themselves in at Wan Chai police headquarters Monday morning on the request of the police.
Both were holding small paper yellow umbrellas -- the symbol of the democracy movement -- as they went into the police station while supporters carrying umbrellas and placards shouted "We want universal suffrage".
"Today Albert Ho and myself were formally arrested," said Wong after she was released.
She said that during questioning police showed her a video and two Facebook photos taken during the protests to illustrate that she had participated in an "unauthorised assembly". Ho said he was questioned over the same allegations.
Both Wong and Ho said the possibility of future charges remained.
"I think this is a kind of political prosecution against those who fight for true democracy," Wong added.
Police had no immediate comment.
A number of protest leaders have already been arrested and only to be released without charge -- including prominent student leaders Joshua Wong and Alex Chow -- in a controversial procedure which some say is harassment.
The street protests, which began in September and lasted for more than two months, kicked off after Beijing said that candidates for the 2017 vote for Hong Kong's next leader would be vetted by a loyalist committee.
Campaigners have described the decision as "fake democracy", but Hong Kong's leadership says that any public vote must take place within Beijing's framework and has granted no concessions over the election process.
Police have said they reserve the right to prosecute those who have been released.
"These pre-arranged arrests are a waste of resources and money," former lawmaker Audrey Eu, who will turn herself in later Monday afternoon, told supporters.
"The police are trying to intimidate Hong Kong people," she added, saying that she was being brought in for inciting and organising an unauthorised assembly.
Former lawmaker and veteran campaigner Martin Lee handed himself in Monday morning to shouts of "Go, Martin, go" from supporters, and was later released.
Lawmaker Charles Mok also turned himself in to police.