A teenager allegedly involved in attacks on five men on the St Kilda foreshore sparked a night of violence when he struck a man with an extendable baton, a court has heard.

Mechac Mukanu is accused of starting a group assault on two men by hitting one of them on the leg with the long metal baton about 10.45pm on December 1, before up to five others repeatedly punched and kicked the pair.

Police allege Mr Mukanu was then one of about 20 African-Australian youths who attacked three men about 15 minutes later, during which the friends were punched, kicked and knocked unconscious, and one had his mobile phone and wallet stolen.

Police arrest youths in St Kilda late last year. Credit:Seven News

Mr Mukanu, 18, on Monday applied for bail in Melbourne Magistrates Court, which heard police had also charged a 17-year-old, who cannot be named, and had another four or five suspects they were yet to arrest.