Hong Kong, Oct 9 : In a first, five teenagers have been sentenced to three years' detention in Hong Kong for advocating overthrow of the Beijing government. The national security law has been used in court against under-18s in Hong Kong for the first time, the BBC reported. Beijing introduced the wide-ranging law to make it easier to prosecute protesters in the city in 2020. Many who defyed the Chinese government have since been jailed, removing much of the political opposition. The court heard the defendants had used social media and street booths to advocate a "bloody revolution" to overthrow the Chinese state in the former British colony, the BBC reported. Judge Kwok Wai-kin said: "Even if one person is incited, Hong Kong's stability and residents' safety could have been greatly harmed," quoted by the BBC. The teenagers (aged between 16 and 19) were members of Returning Valiant, a pro-Hong Kong independence group. Mr Wai-kin said he appreciated the defendants' "age and immaturity", which meant that they were sentenced to a detention facility for young people (also known as a training centre) instead of going to prison. The judge also capped the length of their sentence to three years. How long they remain in custody will remain at the discretion of authorities, the BBC reported. The case also involves two adults, who will be sentenced next month. According to research published by ChinaFile in partnership with Georgetown University, at least 110 people have been arrested under the national security law. Those arrested include protesters, activists and former opposition lawmakers. /IANS