Hundreds of secondary school students protested against Hong Kong's anti-mask law on Tuesday in a show of solidarity with schoolmates arrested for defying the strict new colonel-era legislation.

Forming human chains and staging sit-ins, students across the city voiced support for schoolmates arrested under the new anti-mask law since it was introduced on October 5, reports the South China Morning Post.

Stoking students' anger and prompting calls for a boycott of classes, the city's Education Bureau demanded schools to provide a "rough impression" of the number of students wearing masks to school.

Hong Kong Chief Executive Carrie Lam introduced the anti-mask law in a bid to quell violent protests, which were triggered by the now-withdrawn Extradition Bill and have gripped the city for almost four months.

Breaking the new law would carry a prison sentence of up to one year, or a fine of HK$25,000 ($3,187).

One of the youngsters arrested under the new law so far was a 12-year-old from CCC Kei Long College in Yuen Long, who was protesting in Causeway Bay on the night of October 6.

The girl was seen in video clips widely circulated online when she was arrested along with about 20 other protesters.