Malaysian Prime Minister Najib Razak, responding to the United States Department of Justice’s civil suit over the misappropriation of funds from the state-owned fund 1Malaysia Development Berhad (1MDB), on Thursday said it is best that the legal process be allowed to take its course before a conclusion is made on the matter.

“This is a civil action not a criminal action. Those involved would have to go through the court process in the US,” Najib told reporters at Malaysian palm plantation operator Felda’s open house in Kuala Lumpur.

When pressed over the naming of his stepson Riza Aziz in the court documents, Najib said: “Like anybody else he has rights”, adding that the public must “allow the process to take its course”.

On Wednesday the US Department of Justice filed a civil forfeiture suit to recover US$1 billion that it said were misappropriated from 1MDB.

The US is seeking to freeze assets and profits derived from the film Wolf of Wall Street which Red Granite produced.

Riza is the co-founder of Red Granite.

In addition to Riza, the civil lawsuits filed named two other individuals – Malaysian financier Jho Low, a confidant of the Malaysian premier; and Mohamed Badawy al-Husseiny, a former official at a government fund in Abu Dhabi, United Arab Emirates, that participated in deals with Malaysia’s fund.

Najib also stressed that the country is “serious about good governance”. He added that the government would give its full cooperation to international investigations of the 1MDB case.

The complaint does not name Najib, but it does cite “Malaysian Official 1”, described as a high-ranking government official who oversaw the fund and is a close relative of Riza. 1MDB was overseen by Najib as head of its advisory board.

The US suit alleges that over US$3.5 billion was misappropriated by unidentified Malaysians in transactions over several years using sham corporate vehicles and shell companies to divert funds for personal gain.

The sensational case is shaping up as the largest asset recovery initiative by the US government.

1MDB, which Najib founded in 2009 shortly after he came to office, is being investigated for money laundering in at least six countries, including the United States, Singapore and Switzerland.

Singapore’s central bank said on Thursday authorities have seized assets worth S$240 million in the course of their investigations in relation to various 1MDB-related fund flows for possible money laundering, securities fraud, cheating and other offenses.

The Monetary Authority of Singapore earlier on Thursday disclosed that its preliminary findings show instances of control failings in DBS, and the Singapore branches of StanChart and Swiss bank UBS.

1MDB said in a statement on Thursday “it is not a party to the civil suit, does not have any assets in the United States of America, nor has it benefited from the various transactions described in the civil suit.” The fund said it has not been contacted by the Justice Department or any other foreign agency on the matter.

Malaysia’s attorney-general said on Thursday there has been no evidence from any global probe that show funds were misappropriated from 1MDB and no criminal charges have been made against any individuals.

The A-G had previously in January cleared Najib of any wrongdoing, saying the money was a political donation from the Saudi royal family.

Malaysia’s opposition Parti Keadilan Rakyat on Thursday called on Najib to step down. Meanwhile former Prime Minister Mahathir Mohamad said Malaysians should push for a referendum on Najib’s leadership as he launched a new opposition front made up of ruling party rebels and members of the opposition.