Former prime minister Najib Abdul Razak has defended the letters and other documents he produced as “proof” that the money he received in his personal bank account were donations from a Saudi prince.

“It is important for us to note that all these letters the banks and I received carried Prince Abdulaziz Al-Saud’s letterhead and has the same signature.

“While I cannot confirm what an investigator said about the signature, what I know about the business world is that staff sometimes do sign letters on behalf of their employers,” he said in a Facebook post today.

He was apparently responding to an article by The Edge Weekly earlier today that quoted unnamed investigators saying that the letters were not signed by Prince “Saud Abdulaziz Al-Saud", but a man named Mohammad Abdullah Al-Koman who claimed to be Prince Abdulaziz Majid Al-Saud’s representative.

The source reportedly told the weekly that Mohammad could not provide more information regarding the transactions because it involved "the interests of the Saudi royal family".

"In other words, Mohammad Abdullah told Malaysian investigators that they had to take his word that it came from the Saudi royalty.

"Sources say after the meeting with Mohammad Abdullah, investigators concluded that 'it was not safe to confirm the money from Blackstone (Asia Real Estate Partners) and Tanore (Finance Corporation) were contributions from Saudi Arabia, because it was still unclear and there was a lack of supporting documents',” the report said.

The US Department of Justice (DOJ) had previously claimed that Blackstone and Tanore’s funds originated from 1MDB.

Meanwhile, Najib noted that the article today did not dispute bank documents that he had disclosed. He said these transactions had not been questioned by recipient banks or the Bank Negara either.

These documents showed that the money had come from bank accounts held by the Arab Saudi Ministry of Finance and Prince “Faisal bin Turkey bin Al-Saud”.

Najib also said that The Edge’s article had failed to mention that he had returned RM2.6 billion of the money he received in his bank account, and the transaction was also mentioned in the book "Billion Dollar Whale" by the Wall Street Journal journalists Tom Wright and Bradley Hope.

“This shows that I did not steal or keep billions of ringgit for my personal use and I’m not a rogue, robber, or thief as accused by various parties.

“Although the bank documents on the return and the WSJ book confirms this, Pakatan Harapan leaders and investigators don’t want to talk about it,” he said.

For the record, Malaysiakini had previously raised questions about the identity of “Prince Faisal”, as there is no one with the exact same name as the documents who can be immediately identified as a member of the Saudi royal family.

Meanwhile, the DOJ claimed that of US$681 that was transferred from Tanore to Najib’s account (referred as "Malaysian Official 1" in DOJ’s court documents) in March 2013, about US$620 was returned to Tanore on Aug 26 that year.

It alleged that financier Low Taek Jho’s associate Eric Tan then passed the money through intermediaries and used about US$27.3 million to buy a 22-carat pink diamond pendant necklace for Najib’s wife Rosmah Mansor, plus various artworks.

Najib and Low had denied wrongdoing.