Malaysia's attorney general will cooperate with Swiss counterparts regarding investigations into state fund 1Malaysia Development Berhad (1MDB), the country's top prosecutor said on Saturday.

The attorney-general's comments came after Switzerland's chief prosecutor said he had formally asked Malaysia for help with his probe into possible violations of Swiss law by 1MDB, saying suspected misappropriations amounted to about $4 billion.

Attorney general Mohamed Apandi Ali said the Swiss findings would be reviewed by Malaysia, along with findings of other relevant authorities and internal investigations, to determine the appropriate course of action.

Malaysia's attorney-general had earlier this week cleared Prime Minister Najib Razak, who chairs the 1MDB advisory board, of any criminal offences or corruption regarding deposits into his personal bank account.

Investigations into 1MDB were separate from probes into the bank deposits, Apandi said on Saturday.