HONG KONG (REUTERS) - A student arrested in Hong Kong on suspicion of selling weapons online faces charges of inciting secession under a security law imposed on the city by China three months ago, a senior police officer said on Friday (Sept 25).

Police arrested the 23-year-old man and his mother, 49, on Thursday on suspicion of selling pepperball guns, knives and other offensive weapons, and on further investigation found online posts promoting the use of violence to win independence from China, Superintendent Steve Li of the police's new national security unit said.

Supt Li did not give the names of the suspects.

Beijing imposed a sweeping national security law on June 30 to punish with up to life in prison anything China deems as secessionism, subversion, terrorism and collusion with foreign forces.

Critics of the law say it will erode rights and freedoms in semi-autonomous Hong Kong, while supporters say it will bring stability after a year of social unrest.