Five trade unionists were arrested by Hong Kong police on Thursday in relation to a series of children's books described as "seditious".
Four editors and journalists were separately denied bail by a court as part of a widening crackdown on dissent in the city, which is now again an administrative region of China.
The five arrested citizens are members of the General Association of Hong Kong Speech Therapists, which published the three children's books in question.
The plot of the stories, which are aimed at youngsters aged between four and seven, involves a flock of sheep having to deal with an incursion by wolves from another village. The sheep take various actions like going on strike, or escaping by boat.
Li Kwai-wah, a senior superintendent of Hong Kong Police Force, said the books had "seditious intent" - in that they could allegorise Hong Kong's relationship to the Chinese government.
Li said one of the tales was a nod to the 12 Hong Kong activists who were arrested at sea in December 2012 after taking part in 2019's massive anti-government protests. He added that there was another story about wolves being "cruel and try[ing] to occupy the area" where the sheep lived.
“Of course," he added, "when we prosecute, we are not the ones to prove that these materials have actually caused the inciting to others. And the children, maybe because of the information inside... can turn their mind, develop a moral standard, against society.”
The publication of such books, he said, “brings hatred against the government and administration of justice, and (incites) violence to others."
Police also froze 160,000 Hong Kong dollars ($20,600) in assets linked to the union.
Millions of people in Hong Kong took part in months-long mass rallies in 2019 rallies calling for strengthened civil rights and universal suffrage.
Beijing responded last year with a sweeping national security law that critics say restricts freedoms promised to the former British colony that are not found on mainland China.
Separately on Thursday, a Hong Kong court also denied bail to four top editors and journalists from the now-defunct Apple Daily pro-democracy newspaper. The four were arrested on Wednesday on charges of conspiracy to collude with foreign powers to endanger national security.
Apply Daily ceased operations in June. Some $2.3 million of its assets were frozen and police raided the newspaper’s offices, confiscating hard drives and laptops. Eight people working for the newspaper have been arrested to date.