Hong Kong's Secretary for Security Chris Tang said the six -- all based overseas in countries including Britain and the United States -- had engaged in the alleged crimes of incitement to secession and subversion.
The six included UK-based commentator Chung Kim-wah, former head of a pro-independence group Tony Chung, and Carmen Lau, a member of the Hong Kong Democracy Council.
"As a staunch advocate of Hong Kong nationalism, today's bounty arrest warrants serve as a recognition of my cause," wrote Chung on Instagram.
The move to add more names to Hong Kong's wanted list comes as the city strives to revive its economic growth and international reputation after a years-long crackdown on dissent that has drawn global criticism.
China and Hong Kong authorities have defended the clampdown under sweeping national security laws, saying stability has been restored after mass pro-democracy protests in 2019.
Tang said the six pro-democracy campaigners had engaged in activities including giving speeches, social media posts and lobbying for Hong Kong officials and judges to be sanctioned by foreign governments, that had endangered national security.
Others were deemed to have advocated Hong Kong's independence from China. Hong Kong, a former British colony for over 150 years, returned to Chinese rule in 1997 and is considered an inalienable part of China.
"Instead of celebrating X’mas, it (Hong Kong) is taking a major step to escalate its transnational repression campaign," wrote Anna Kwok, a U.S. based Hong Kong activist.
There are now a total of 19 opposition figures on the city's wanted list including lawyers Kevin Yam and Dennis Kwok, former lawmaker Ted Hui and activists Nathan Law and Frances Hui.
Hui had HK$800,000 of his money confiscated from an unspecified bank in the city, Tang said. Notices bearing black and white photographs of the "fugitives" have been posted in public including at Hong Kong's international airport.
Seven "absconders", including Hui, who are now based overseas, also had their passports revoked under a fresh set of national security laws known as Article 23, enacted this year.
"They will become someone without an identity," Tang told reporters.
