The activists were formally arrested on Wednesday, according to the Hong Kong Free Press. The charges were brought a day before China’s National Day. For the celebration, strict security measures were enforced in the region due to protests.
The activists were caught after leaving Hong Kong’s coast, 43 miles southeast of the city.
They were then handed over to police forces in Shenzhen in China.
According to the families and lawyers of the activists, the authorities did not provide much information on the arrests until they pressed formal charges for making an illegal border crossing.
Two of the arrested suspects were charged with helping the others “escape” from Hong Kong.
Since Beijing enforced a national security law earlier this year in the autonomous city, more people have been leaving Hong Kong.
The new security law in Hong Kong criminalises any act of secession, subversion, terrorism and collusions with foreign forces.
The number of Hongkongers seeking residency in Taiwan rose to 892 in July after the security law was implemented, according to Taiwan’s National Immigration Agency.
The increase of people trying to leave Hong Kong for Taiwan in July was the highest number this year.
China celebrated its national day on Thursday which commemorates the founding of the People’s Republic of China in 1949.
More than 60 people were arrested on Thursday in Hong Kong after small crowds emerged in protest of the celebration.
They protesters were arrested in Causeway Bay and were accused of participating in an unauthorised assembly, according to the police.
On Thursday, Hong Kong’s chief executive Carrie Lam said her Government would not be daunted by the international sanctions imposed on it in response to the national security law.
She said: “Over the past three months, the plain truth is – and it is obvious to see – that stability has been restored to society while national security has been safeguarded, and our people can continue to enjoy their basic rights and freedoms in accordance with the law.
“So, no matter how severe some foreign governments, holding double-standards, are going to level unjustified accusations against the authorities in charge of implementing the national security law, or aggressively imposing further sanctions against HKSAR [Hong Kong special administrative region] officials responsible for safeguarding national security.
“I and my relevant colleagues will continue to discharge our duty to safeguard national security in accordance with the law without fear or anxiety.”
Many activists called for the release of the 12 Hongkongers who were caught allegedly fleeing to Taiwan.
The Hong Kong government refused to intervene in the case saying the group, which included a 16-year-old child, should face mainland justice.