Yahoo Chairman Roy Bostock, also a target of shareholder frustration, informed Bartz about the move over the phone, according to an email the outgoing CEO sent from her iPad that was obtained by the All Things D technology blog. The blog first reported Bartz's ouster.

A Yahoo spokesman didn't immediately respond to a request for comment late Tuesday.

Macquarie Securities analyst Ben Schachter called the handling of Bartz's departure “unseemly” and interpreted it as a sign of even more drama to come at Yahoo.

In a research note late Tuesday, Schachter predicted there will be a wide range of conjecture about Yahoo's future, with the most likely speculation centering on Yahoo as a takeover target during a vulnerable time.

Alternatively, Yahoo could make a bold move itself by trying to buy the online video site Hulu.com, which is already talking to suitors, or trying to sell its 43 percent stake in the Alibaba Group, one of China's most prized Internet companies. Bartz's tense relationship with Alibaba CEO Jack Ma had fed investor dissatisfaction about her leadership.

In a Tuesday statement, Yahoo said it is undergoing a “comprehensive strategic review” in its latest effort to give investors a reason to buy its stock but didn't offer details.

Bartz, 63, led an austerity campaign that helped boost Yahoo's earnings, but the company didn't increase its revenue even as the Internet ad market grew at a rapid clip.

The financial funk, along with recent setbacks in Yahoo's online search partnership with Microsoft Corp. and the Alibaba investment, proved to be Bartz's downfall. Her ouster comes with 16 months left on a four-year contract that she signed in January 2009.

That contract entitles her to severance payments that could be two to three times her annual salary and bonus, along with stock incentives she received during her tenure. Bartz received a $2.2 million bonus to supplement her $1 million salary last year.

Yahoo has now replaced three CEOs in a little over four years. During that time, Yahoo has lost ground in the Internet ad race to online search leader Google Inc. and Facebook even though its website remains among the world's most popular.

Known for her no-nonsense leadership and sometimes gruff language, Bartz arrived at Yahoo as a respected Silicon Valley executive who had won praise for turning around business software maker Autodesk Inc. But she had no previous experience in Internet advertising, the main way Yahoo makes money.