1MDB says it has not benefitted from the transactions listed in the United States Department of Justice lawsuits to seize assets purchased using funds allegedly siphoned from the state investment firm.

The US Department of Justice filed the lawsuits in Los Angeles yesterday to seize assets worth more than US$1 billion, out of the US$3 billion US investigators believe were "defrauded" from the Malaysian public.

"1MDB highlights that 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.

"Furthermore, 1MDB has not been contacted by the US Department of Justice or any other foreign agency in relation to their investigations.

"As previously stated, 1MDB will fully cooperate with any foreign lawful authority, subject to international protocols governing such matters and the advice of the relevant domestic lawful authorities," it said in a statement.

Those named in the lawsuits are Prime Minister Najib Abdul Razak's stepson Riza Aziz, their family friend and businessman Low Taek Jho, better known as Jho Low, and two former Abu Dhabi officials.

Although Najib is not named in the lawsuit, one person named in the documents is referred to as 'Malaysian Official 1'.

The Wall Street Journal quoted a source familiar with investigation as saying that the 'Malaysian Official 1' refers to Najib.

Najib has consistently denied any wrongdoing in connection with the 1MDB scandal.

Asked why the person was not named, US attorney-general Loretta E Lynch told a press conference on Wednesday that the civil complaint traces the movement of the assets and would only "allege what we need to allege to obtain what we need to obtain".

Asked if there was an arrangement not to name Najib, Lynch said: "Our agreement is only to draft the complaint as we do in civil forfeiture matters and it's a complaint against the actual money or assets as opposed to against an individual.

"We don't have announcements on anyone not named so far.

"So this will be a complaint that seeks to restrain and forfeit the specific assets mentioned," she said at a Department of Justice press conference in Washington DC that was streamed live online.