KUALA LUMPUR - Malaysia's Court of Appeal on Monday began hearing a bid by former Prime Minister Najib Razak to set aside his conviction on corruption charges in a case linked to a multi-billion dollar scandal at state fund 1MDB.

Najib, who was voted out in a historic 2018 election, faces several trials over allegations that $4.5 billion was stolen from 1Malaysia Development Berhad (1MDB), a state fund he co-founded in 2009. He has plead not guilty to all charges.

Last year, Najib was sentenced to 12 years in jail and a $50 million fine after being found guilty of criminal breach of trust, abuse of power and money laundering for illegally receiving about $10 million from SRC International, a former 1MDB unit.

The sentences were stayed pending an appeal.

Najib's lawyer Muhammad Shafee Abdullah, in his opening remarks on Monday, argued that the trial judge had erred by including additional matters in his final ruling which had not originally been part of the case against the former premier.

"We will be contending that this was highly improper and in fact, prejudicial towards our client," Muhammad Shafee said.

Muhammad Shafee had earlier requested for the appeal to be adjourned for another month, saying he needed more time to obtain documents relevant to Najib's defence from the United States and Singapore. The court, however, rejected the request.

The court has fixed 12 days between April 5 and 22 to hear the appeal. If Najib loses the bid, he can still appeal at the Federal Court, Malaysia's highest tribunal.

Prosecutors have said more than $1 billion of 1MDB funds made its way into Najib's personal accounts, over which he faces a total of 42 criminal charges.

At least six countries have opened investigations into 1MDB, in a globe-spanning scandal that has implicated high-level officials and major financial institutions.

In recent months, Malaysia has recovered more than $3 billion from U.S. bank Goldman Sachs, audit firm Deloitte, and Malaysian banking group AmBank in separate deals to settle claims linked to 1MDB probes. 

($1 = 4.1440 ringgit)

(Reporting by Rozanna Latiff; Editing by Martin Petty) ((rozanna.latiff@thomsonreuters.com; +61 3 9492 9423 ; Reuters Messaging: @rozlatiff on Twitter))