More than US$1 billion ($1.4 billion) was deposited in the bank accounts of Malaysia's Prime Minister Najib Razak – millions more than was previously identified, according to the Wall Street Journal, quoting unnamed people familiar with the matter.
The newspaper published the allegation hours after Malaysia's former leader Mahathir Mohamad quit his country's ruling party, saying he did not want to be associated with a group that is seen as supporting corruption under Mr Najib's leadership.
Calls for people power to oust Malaysia PM
The streets of Kuala Lumpur are filled with protesters for a second day demanding the resignation of Prime Minister Najib Razak over a financial scandal.
The Wall Street Journal said millions of dollars arrived in Mr Najib's accounts in 2011 and 2012, citing two people familiar with flows into the accounts and a person familiar with one overseas investigation.
Mr Najib, a British-educated son of a former Malaysian prime minister who has close ties to the Australian government, denies any wrongdoing and says the allegations are part of a plot to topple his government.
The report will intensify pressure on Mr Najib in the ruling United Malays National Organisation (UMNO) where powerful division chiefs have refused to move against him.
The Prime Minister has purged key party members who have questioned the source of the money, put a lid on investigations into his actions and cracked down on media outlets that looked into the case.
Kadir Jasin, an influential commentator in Kuala Lumpur who has supported a fierce campaign against Mr Najib, described Dr Mahathir's resignation as a "kick in the groin of UMNO".
Asked about the resignation before travelling to Saudi Arabia for official meetings, Mr Najib smiled but made no comment.
Dr Mahathir, 90, who served as prime minister and president of UMNO for 22 years before stepping aside in 2003, said he has no plans to start a new party.
"I want to leave UMNO because it is no longer UMNO," he said.
"It's a party dedicated to protecting Najib. I can't be a member of such a party."
Last week Muhyiddin Yassin, a prominent UMNO member and former deputy prime minister, called on Mr Najib to step down over the "dark episode" of his financial dealings involving Malaysia's heavily indebted sovereign fund 1Malaysia Development Berhad, which the prime minister founded and oversees through an advisory board.
Mr Najib's loyalists in UMNO then suspended Mr Muhyiddin as UMNO's deputy president.
Mr Najib has declined to comment on the latest Wall Street Journal allegation.
Malaysia's attorney-general recently claimed that US$681 million that was deposited into his accounts in 2013 was a donation from a member of Saudi Arabia's royal family, and most was returned.
But the Wall Street Journal and the London-based Sarawak Report earlier reported the money flowed through a series of international transactions from the sovereign fund.
Investigations into the fund are underway in the United States, Singapore, Hong Kong and Switzerland.
Mr Najib has not directly explained the source of the money or what happened to millions of dollars that is still publicly unaccounted.
But the Prime Minister has declared the matter closed and urged Malaysians to unite and move forward from the scandal that has dogged his leadership for months.
A Malaysian government spokesperson lashed out at the Wall Street Journal over its report, accusing the newspaper of becoming "a willing vehicle for certain political actors who are seeking to damage the prime minister and Malaysia for personal gain."
The spokesperson said multiple lawful authorities who conducted exhaustive investigations have verified the funds were a donation from Saudi Arabia.
"It is therefore telling that the Wall Street Journal, and its sister entities, are continuing their attacks and trying to link 1MDB (the sovereign fund) to the donation," the spokesperson said.
"They keep repeating the same old allegations without providing evidence; they keep relying solely on anonymous sources that might not even exist; and they keep choosing to omit key known facts."