SINGAPORE (BLOOMBERG) - Noble Group Ltd., the commodity trader that has attracted criticism for its accounting practices, bought back a second batch of 25 million shares as it seeks to install confidence among investors.

The company made the purchase on Friday at an average price of $0.6728, Hong Kong-based Noble said on Monday in a filing to the Singapore Stock Exchange, where its stock is listed. It's shares rose 0.7 per cent to $0.69 as of 09:22 local time. Noble also bought 25 million shares on June 11.

Noble's stock slid 2.8 per cent slide on Friday, having fallen as much as 7.8 per cent on the day. Its shares have closed higher only twice this month, including on the day of the first buyback.

Noble founder and chairman Richard Elman said in a public letter to shareholders on June 11 that the company is battling against rumors and inaccurate statements and pledged to "right the damage" to its share price.

An anonymous group that calls itself Iceberg Research sparked a debate about accounting at the Hong Kong trader with a series of critical reports since February. Muddy Waters LLC then said in April it had taken a short position on the stock. Noble has rejected all of the criticisms.

Noble's stock is down 43 per cent since Iceberg's first report.