SINGAPORE - Mainboard-listed Noble Group shares came under heavy selling pressure on Monday, continuing a rout triggered by allegations of accounting malpractice by unknown firm Iceberg Research.

Its shares were the most active on the Singapore Exchange, trading down 4.5 cents or 4.6 per cent, to 93 cents at about 9:45am, with 29 million shares changing hands.

The Hong Kong-based commodities firm saw its shares plunge 8 per cent last Friday after the company reported a shock US$240 million loss for the fourth quarter ended Dec 31, 2014, its first quarterly loss in three years, largely due to an unexpected US$438 million write-off.

Noble also faced a second report on its accounting practices from Iceberg last week. Noble's Chief executive officer, Yusuf Alireza, said that a displeased former employee is likely to be the one behind the damning reports.