HONG KONG — The Malaysian authorities charged Najib Razak, the former prime minister, with three counts of money laundering on Wednesday, the latest escalation in an inquiry involving billions of dollars diverted from a state investment fund.

The charges came a day after Malaysia’s attorney general announced that a $250 million yacht, which prosecutors say was bought with money stolen from the fund, had been returned to Malaysia from Indonesia, where it was seized in February.

The new charges are linked to three electronic transfers worth a total of $10 million from a onetime unit of the investment fund, 1Malaysia Development Berhad, that prosecutors say were made into Mr. Najib’s bank accounts.

That is only a small fraction of the fraud alleged to have been carried out. United States prosecutors have said that at least $4.5 billion from the fund, known as 1MDB, was laundered through American financial institutions and misspent by Mr. Najib, his family and associates.