However, analysts remain unconvinced that the share purchases will be enough to help the company fight off short-sellers. According to data by Jefferies, the outstanding shares held by short sellers on Noble Group increased from 50 million shares in April to around 400 million now.  "[Despite the third buyback,] we continue to see the possibility of a dead cat bounce in Noble's shares. Near-term oscillators continue to point to the bearish side, with the 14-day Relative Strength Index (RSI) still capped below 50 and the Moving Average Convergence/Divergence (MACD) line remaining under the signal and zero line," IG's market strategist Bernard Aw wrote in a note released Tuesday, adding that the 50-day moving average at S$0.828 will act as a "formidable barrier" for the stock.  A dead cat bounce is a short-lived rally, often caused by short-covering, in a stock suffering from a prolonged decline.  Most importantly, Aw said that weak underlying fundamentals remained the key obstacles for a recovery in the battered stock.  "The reality is that Noble is under pressure from several fronts, including a falling profit margin, a slowdown in commodity trading as well as issues relating to corporate governance and transparency. Piecemeal measures such as share buybacks are unlikely to relieve the downward pressure as long as the backdrop does not improve substantially," Aw said.  For CMC Markets' Nicholas Teo, the sustainability of the rebound depends on how aggressive Noble Group is with their share purchases.  "The rebound is relative on how much more the company wants to buy since they have in their authority to buy up to 673 million shares based on their filing. The shares they have bought thus far, with no pun intended, is only the tip of the iceberg," the Singapore-based analyst told CNBC by phone. Noble Group now holds more than 62 million shares by way of market acquisition.  "The aggressive buying has shown a floor in the share price and markets recognize that, regardless of whether the rebound is sustainable or not, so short sellers may not be so keen now. But the rebound above S$0.70 may also allow short sellers to have the opportunity to have another kick in the can," Teo added.  Shares of Noble Group have lost about 40 percent since February when anonymous group Iceberg Research released a series of critical reports on the Hong Kong trader's accounting practices. U.S. short seller Muddy Waters dealt another blow to the company in April after saying it had taken a short position on the stock.  Last week, S&P downgraded the company's rating outlook to negative from stable, citing that the higher risk nature of Noble's trading positions could result in more volatile earnings and profitability for the company.
A fresh round of stock buyback put some color back into shares of Noble Group, but analysts warn that the upside may be just a "dead cat bounce."