Beijing: Clashes with Hong Kong students by mainland Chinese studying in Australia are "understandable and reasonable" but Chinese students should abide by local laws, the Foreign Ministry in Beijing has said.

Chinese state media attacks on Hong Kong protesters continued on Tuesday, including claims that they are colluding with western governments, even though Hong Kong chief executive Carrie Lam welcomed the "peaceful" nature of Sunday's massive march, and offered to establish a "dialogue platform" with protesters.

Supporters of Hong Kong's democracy protesters clash with pro-China groups in Melbourne. Credit:Justin McManus

Meanwhile, a British consulate official in Hong Kong was detained in the mainland Chinese city of Shenzhen, and three people were hospitalised after being attacked with a knife at a Lennon Wall in Hong Kong. A man alleged to be the knife attacker was arrested by Hong Kong police trying to cross the border to mainland China on Tuesday.

Hong Kong police have also announced that they had arrested two of their own officers on suspicion of assault after video was released by pro-democracy politicians on Tuesday that showed the officers punching a 62-year-old man in hospital after he had been arrested for drunk and disorderly behaviour. Police misconduct has been a major complaint of the democracy protesters.