Two men from Singapore and Malaysia faced life in an Australian prison Monday after police charged them over more than five kilos (11 pounds) of heroin found hidden in Chinese books.

The men, a 49-year-old Singaporean and a 32-year-old Malaysian, were questioned by customs officials after they arrived at Melbourne Airport on a flight from Kuala Lumpur on Friday.

Australian Federal Police (AFP) linked them to two packages which were found in Melbourne's central business district, where the men were due to stay.

"One package was examined and was found to contain 22 sealed Chinese books," police said in a statement.

"Following an examination of one of the books, AFP officers seized 350 grams of a white powdery substance, which initial testing identified as heroin."

Testing is ongoing but police suspect a total of 5.6 kilos of the drug was concealed within both packages.

The men were charged with attempting to possess a commercial quantity of a drug -- an offence which has a maximum penalty of life imprisonment and/or an Aus$825,000 (US$860,000) fine.