Two men jointly charged in Kuala Lumpur court with six counts of criminal breach of trust over $1.58bn.

Former Prime Minister Najib Razak and his top civil servant at the treasury have been jointly charged with the misuse of some 6.6 billion ringgit ($1.58bn) in government money, as Malaysian prosecutors step up their crackdown on corruption.

Najib and Mohd Irwan Serigar, who was the secretary-general of the treasury, appeared in court in Kuala Lumpur on Thursday to face six counts of criminal breach of trust.

The two pleaded not guilty to all charges. Each carries a jail term of as many as 20 years, a fine, and whipping. Neither Najib or Irwan would be subject to caning because of their age.

Public anger over the scandal at state-fund 1MDB triggered the downfall of Najib’s government in May’s general election and the country’s first change of power in 60 years. The new administration under veteran leader Mahathir Mohamad has moved quickly to investigate corruption and what happened at 1MDB.

Prosecutors alleged the two men committed the breach of trust offence with $53m of government money that was meant for the Kuala Lumpur International Airport, and $312m that was supposed to be used in a subsidy and cash aid programme.

They also committed the offence with $1.2bn of other government funds, prosecutors said.

Local media reported the money was used to settle 1MDB’s financial obligations to Abu Dhabi-based International Petroleum Investment Company (IPIC).

Najib is already facing 32 charges of money laundering, corruption, and breach of trust involving more than $551m in transactions linked to 1MDB. His trial on those offences is due to start next year.

Thursday’s charges are the first to be brought against Irwan, who was arrested by the country’s anti-graft agency on Wednesday and held overnight.

Authorities in the US allege $4.5bn was syphoned from the 1MDB fund and about $700m was diverted into Najib’s personal bank accounts.

Najib’s wife, Rosmah Mansor, and his former deputy, Ahmad Zahid Hamidi, have also been charged with corruption and money laundering. They have pleaded not guilty.