The demonstrations started peacefully, but the situation changed soon with students.(File Photo)

A 12-year-old boy became the youngest protester to be convicted in the six-month-long pro-democracy protests in Hong Kong as a court in the former British colony reserved orders to place him under counselling and supervision for up to three years.

The probation order, if clamped, would also leave the minor with a criminal record, Hong Kong-based South China Morning Post reported on Thursday.

Since the pro-democracy protests began about six months ago over the Hong Kong government's attempts to bring an Extradition Bill, this round of protests have caught the attention of China and the world for their mass public participation, specially the youth and students.

The demonstrations started peacefully, but the situation changed soon with students, including those in the age group of 12 to 16-years, displaying raw power in destroying public property.

The protests are continuing even though the government has withdrawn the Extradition Bill. Over 4,500 people mostly students have been arrested so far in the protests.

The protestors are demanding pro-China Chief Executive Carrie Lam's resignation, inquiry into police brutalities and universal franchise of ''one person one vote'' with freedom for all the locals to contest elections for the local legislature.

The convicted boy, whose name has been withheld for legal reasons, pleaded guilty on Thursday for vandalising a police station and railway interchange last month.

His lawyer Jacqueline Lam asked the court to give the minor a second chance, saying he was remorseful since being charged and only acted on impulse at the time of the offences, which involved spraying obscene graffiti.

"He knows he made a serious mistake," said Lam, urging the court to pass a sentence that would not leave someone so young with a criminal record.

"It has been an important lesson to him, as he was detained overnight at a police station after arrest," Lam said.

The student admitted two counts of criminal damage at West Kowloon Magistrates'' Court for vandalising Mong Kok Police Station and an exit at Prince Edward MTR station on October 3, the Post's report said.

Lam told Magistrate Edward Wong Ching-yu that the boy, whose parents have been divorced and he is living with his grandmother, was so remorseful he only left his home to attend school after his arrest and had not played basketball or practised dragon dance since.

But Magistrate Wong appeared unmoved, reserving the option to impose a probation order, where the boy would be under the counselling and supervision of a probation officer for up to three years. The boy will be sentenced on December 19, the report said.