SINGAPORE (Reuters) - Iceberg Research, the anonymous research outfit that has criticised commodity trader Noble Group for its accounting practices, said it sees more writedowns the company's investment in Yancoal Australia.

Iceberg's latest statement came after Noble on Thursday pledged to provide more disclosure and issued a strong rebuttal to accusations of improper accounting made by Iceberg.

"The carrying value of Yancoal is now US$322 million and the market value of the 13 per cent stake is worth US$7 million. There is still a US$315 million gap that Noble will have to recognise," it said in its latest research.

Noble said this week it only decided to take a US$200 million impairment charge relating to its 13 per cent stake in ASX-listed Yancoal on the day of its earnings release. It reported a quarterly loss due to Yancoal and other writedowns.

Iceberg has not disclosed the identity of the writer of its report on Noble, only saying that it has been acting as a whistle blower and not as a short seller.

It said it will give more details about the identity of the writer after the third report, following Noble's statement that the contact person for the company behind the report is a former credit analyst at Noble whose job was terminated in 2013.