MELBOURNE, Sept 18 (Reuters) - Australia's police arrested 235 people in Melbourne and 32 in Sydney on Saturday at unsanctioned anti-lockdown rallies and several police officers were injured in clashes with protesters. Victoria police said six officers required hospitalisation. Several officers were knocked to the ground and trampled, the police said and television footage showed. About 700 people managed to gather in parts of Melbourne, as 2,000 officers made the city centre virtually a no-go zone, setting up checkpoints and barricades. Public transport and ride shares into the city were suspended. In Sydney, riot squad officers, highway patrol, detectives and...