The US Federal Bureau of Investigation (FBI) has praised the Malaysian Anti-Corruption Commission (MACC) for its courage in the 1MDB probe.

An article on FBI's official website cited its International Corruption Unit chief Special Agent Darryl Wegner as saying the MACC "showed 'tremendous courage' in pursuing the investigation, which was led by the FBI's international public corruption squad in New York".

"Today's action sends a message to corrupt foreign officials. The FBI, together with our international partners, will find these individuals and root out their corruption.

"We are working very hard to make sure that the US will not be a safe haven for these types of crimes," Wegner added.

The FBI has been working together with the US Department of Justice (DoJ), which yesterday filed civil lawsuits seeking to seize more than US$1 billion in assets, allegedly obtained with funds siphoned from 1MDB.

The DoJ's suits cited evidence that appear similar to MACC's own findings in its 1MDB probe.

This includes evidence that in March 2013, US$681 million of 1MDB funds had been deposited into the account of an unnamed high ranking public officer dubbed "Malaysian Official 1".

Similarly, attorney-general Mohamad Apandi Ali had in January this year acknowledged that US$681 million had been banked into Prime Minister Najib Abdul Razak's accounts in March 2013.

Apandi said Najib had returned US$620 million of the funds, which he chalked down to a personal donation from a member of the Saudi Arabian royal family.

Saudi Foreign Minister Adel Al-Jubeir later confirmed that a donation was made to the Malaysian prime minister.

Apandi also concluded that Najib had not committed any wrongdoing and ordered no further action on the MACC's investigations.

Critics have said that the MACC's probe had been hampered by Apandi's refusal to grant the graftbuster permission to seek mutual legal assistance from other countries in its pursuit for evidence against 1MDB.

The government has denied elements of a cover-up, while Najib and his supporters blamed the allegations on those conspiring to topple him from power.