Twenty people were arrested overnight for drug possession in a police crackdown on some of Melbourne's most notorious night-time entertainment precincts.

Uniform and plainclothes police and the dog squad stormed Chapel Street, Toorak Road and the St Kilda and Prahran areas between 11pm Saturday and 5am Sunday.

Drugs seized during the operation included cannabis, amphetamine, cocaine, ketamine and MDMA.

Police targeted areas around nightclubs and bars including Lucky Coq on Chapel Street, Circus Bar on Commercial Road and Pawn and Co at Greville Street in Prahran.