A Brazilian man who has been charged with killing his Brazilian ex-girlfriend in Australia was transferred from a police station to a prison for pre-trial detention on Tuesday evening.

The police department said on Monday that Mario Marcelo Ferreira dos Santos Santoro had been formally indicted on charges of killing Cecilia Muller Haddad in late April.

He was arrested on Saturday in Rio's Botafogo neighbourhood, hiding in a relative's home, authorities said.

Police have 30 days following the arrest to gather more evidence before prosecutors present the case against dos Santos Santoro for trial.

Police said he is alleged to have strangled Haddad, whose body was found April 29 in Sydney's Lane Cove River.

Authorities said evidence indicates the suspect fled to Brazil immediately after the killing.