By Agence France-Presse
A prosecution witness told a district court that Singaporean Yeo Jiawei, 33, left his job at the local branch of Swiss bank BSI in 2014 to work with Low Taek Jho, a family friend of the Malaysian leader, and they conducted business in a secretive way.
Allegations of misappropriations of billions of dollars from 1MDB through money-laundering have triggered a corruption scandal in neighbouring Malaysia that has embroiled Najib. The prime minister, 1MDB and Low have strongly denied any wrongdoing.
The witness, ex-BSI managing director Kevin Swampillai, said Yeo travelled on a private jet used by Low and exchanged secretive text messages with the businessman.
"When Yeo worked with Low Taek Jho and consulted with his associates, there was a great degree of secrecy around what they did, how they spoke to each other, and apparently fictitious names were used when referring to certain individuals," Swampillai told the court.
Low, also known as Jho Low, had helped set up 1MDB and played a key role in its decisions.
Yeo is on trial on charges of obstructing Singapore's investigation into the 1MDB scandal. Other charges will be tried later.
Apart from Singapore, the scandal is also being investigated by Switzerland -- because Swiss banks were allegedly used to transfer illicit funds -- and the United States, where assets using alleged laundered 1MDB money were purchased.
Swampillai said Yeo once sent him a picture from a private plane showing Low.
He said Yeo and Low also travelled to Las Vegas last year to watch the fight between undefeated US boxing champion Floyd Mayweather and the Philippines' Manny Pacquiao.
Singapore prosecutors said Monday that Yeo, the first person to be tried anywhere in relation to the 1MDB case, "played a central role in many activities connected with the money-laundering case".
They said the case involved the cross-border transfer of "staggering" amounts of money.
Singapore authorities have seized nearly $180 million in assets in relation to their probe, half of them linked to Low. They have closed the local branches of BSI and another Swiss bank, Falcon, found to be involved in illicit fund transfers.
In July the US Justice Department filed lawsuits in the United States alleging a massive international conspiracy by Najib's relatives and associates to steal billions from 1MDB.
Swiss Financial Market Supervisory Authority FINMA said in October that during its investigation from 2012 to 2015, it found that "assets amounting to approximately $3.8 billion were transferred to accounts at Falcon and associated with the 1MDB Group".