HONG KONG (BLOOMBERG) - The Hong Kong government has outlawed a key slogan chanted by hundreds of thousands of protesters, in the latest sign that the authorities plan to use a new Beijing-drafted national security law to enforce limits on free speech.

In what it called a "solemn statement" late on Thursday (July 2), the Hong Kong government said the rallying cry "Liberate Hong Kong! Revolution of our time!" was now illegal under the law barring secession, terrorism, subversion of state power and collusion with foreign forces.

The sweeping law, which carries prison sentences as long as life in prison, was made public only as it took effect late Tuesday.

The government had said earlier on Thursday that banners and chants calling for "Hong Kong independence" were now illegal, without specifying that that prohibition also applied to the more widely used "Liberate Hong Kong!" slogan.

Independence was never included among the "Five Demands" sought by protesters last year, only meaningful elections.

"The slogan 'Liberate Hong Kong, the revolution of our times' nowadays connotes 'Hong Kong independence,' or separating the Hong Kong Special Administrative Region from the People's Republic of China, altering the legal status of the HKSAR, or subverting the State power," the government said.

The Hong Kong police arrested 370 people at protests against the legislation on Wednesday, the 23rd anniversary of Hong Kong's return to Chinese rule.

Ten were detained under provisions of the new national security law.

"Until the offenders are charged and tried, it is unclear to both police and the public whether their behaviour does in fact violate the new law - and if so, how steep the penalties will be," Eurasia Group political risk analysts Andrew Coflan and Allison Sherlock wrote in a note to clients.

"In the meantime, officers seem to be targeting demonstrators making direct calls for independence, while others continue to be arrested for violating public order."