China's top prosecution body has cast a thin, bespectacled teenage activist from Hong Kong as a pro-independence advocate backed by the United States in an online video that warns against uprising movements across the country.

Joshua Wong, a student leader who rose to fame at the age of 15 for forcing the Hong Kong government to shelve a pro-China national education scheme in schools, appears in a video with a caption that says "American-led Western power".

The video, released on Aug. 1 by the Supreme People's Procuratorate via its official Weibo account, depicts harrowing images of refugees from Central Asia, the Middle East and Eastern Europe dying or in horrific conditions. The video then contrasts this with pictures of a strong and stable China.

Hong Kong, Taiwan, Tibet and Xinjiang, are singled out, as are dissident activists who are "damaging China's internal stability and harmony by hook or by crook. Behind all these incidents, we can often catch a glimpse of the dark shadow of the Stars and Stripes," the video states.

Wong, now 19, said on his Facebook page that he viewed the video statements as a joke and had not advocated for Hong Kong independence.

The democracy activist was found guilty by a Hong Kong court on July 21 for unlawful assembly related to demonstrations that paralyzed key arteries of the Chinese-ruled city in 2014.

The 79-day "Occupy Central" street demonstrations crippled parts of Hong Kong and were one of the boldest populist challenges to Beijing's Communist Party leaders in decades.

Hong Kong is technically part of China but governed by separate laws under a "one country, two systems" framework agreed with the British when it was handed back from colonial rule in 1997.

Relations between the two have frayed in the year and a half since the end of the protests.

The video ends with a message warning watchers to "Protect China, be cautious against color revolutions."