Shares of Alibaba.com tumbled as much as 10 percent after an internal probe prompted resignations of its top executives and forced the company to clean up a vendor mess that defrauded buyers.

China's biggest e-commerce company, founded by billionaire and former school teacher Jack Ma, now faces the challenge of coping with the abrupt replacement of its CEO and COO and with revamping its payment and credit-ranking system to prevent the fraud it announced on Monday.

Alibaba.com's shares fell by as much as 9.6 percent to HK$15.08 and ended down 8.6 percent, logging the biggest fall since September 2009, during the global financial crisis. The broader Hong Kong market shed 2.1 percent.

Alibaba.com, which dominates China's business-to-business Internet space, needs to rework its business model, but most analysts say the latest management shakeup will have limited impact on its financial performance in the next few quarters.

It may shake up some of the confidence level of the buyers, mostly international buyers, said Alicia Yap, an analyst with Citi in Hong Kong.

Volume in Alibaba.com surged to 71 million shares, nearly five times the average traded over the past 30 days. Before Tuesday's fall, the shares were up 20 percent so far this year.

Morgan Stanley cuts its Alibaba rating to equal-weight, while Mirae downgraded it to hold due to challenges faced by the new CEO to revamp its payment and credit-ranking systems.

However, CLSA and Yuanta Research retained their buy recommendations on the stock, while Macquarie held on to its price target of HK$12.50.

Jonathan Lu, a 41-year-old who heads up unlisted online retailer Taobao, will take over as CEO of Alibaba.

Analysts said a key challenge that Lu faces was to train up its employees to winnow out dodgy suppliers.

It's also to do with the integrity of the employees. Without the help of the internal employees, a lot of these accounts will actually not be able to pass, Yap said.

Standard Chartered analyst Don See said in a report the move could possibly pave the way for a possible injection of Taobao's assets into Alibaba.com.

On Monday, Alibaba.com CEO David Wei Zhe and Chief Operating Officer Elvis Lee Shi-huei resigned after a noticeable increase in fraudulent transactions at the Chinese e-commerce firm's website.

The company said Lee and Wei were not personally involved in any of the claims and that they had made good faith efforts to address the problem, but were resigning to take responsibility for a systemic breakdown.

We are concerned that the company's overseas customers will be less willing to transact business with the company's CGS (China Gold Supplier) members as the level of trust in the platform declines, said Paul Wuh, an analyst at Samsung Securities.

Alibaba.com's so-called China Gold Suppliers is a network of high-volume members. Samsung is maintaining a sell rating for Alibaba's stock with a target price of HK$11.

Alibaba.com, a unit of Alibaba Group, 40 percent owned by Yahoo! Inc, focuses on connecting small and medium-sized companies at home and abroad on sourcing for goods, such as garments, computers and machinery.

The company, founded by Jack Ma, who has been featured on the covers of magazines such as Forbes, competes with Global Sources in China's roughly 1.7 billion yuan business-to-business marketplace.

China's e-commerce market is growing rapidly, with online retail sales expected to surge to $159.4 billion by 2015 from $48.8 billion, according to industry forecasts.

In November, Alibaba.com reported a record quarterly profit of 366 million yuan ($55 million) in July-September, though the company sees slower growth due to new service price hikes and as China's exports growth eases.