The surprise departure of Citigroup Inc's Chief Executive Vikram Pandit could be a sign of near-term uncertainty for the stock, but the options-market shows many investors are bullish on the shares in the longer term.

A day after a strong earnings report, Citigroup unexpectedly announced on Tuesday that Pandit had resigned along with Chief Operating Officer John Havens. Michael Corbat, previously chief executive for Europe, Middle East and Africa, will succeed Pandit.

Citigroup shares fell ahead of the opening bell on the announcement, but recovered to close up 1.6 percent at $37.25 on a busy day of trading.

The news also sparked a burst of option activity on Citigroup, led by the trading of calls, contracts that give the right to buy the shares at a fixed price by a certain date.

"I think Citi option traders were surprised initially on the timing of the announcement more than anything," said TD Ameritrade chief derivatives strategist J.J. Kinahan.

Options turnover on Citi was 2.6 times the average daily levels with 205,000 calls and 148,000 puts traded at the close, according to options analytics firm Trade Alert.

Nearly 41 percent of the volume on Tuesday afternoon was in the soon-to-expire October options, led by the October $37 strike calls and puts, Trade Alert data showed.

Citigroup's implied volatility, a barometer of perceived risk of future stock movement, is down across options contracts expiring in coming months. The exception are October options, which expire after Friday's close, according to options analytics firm Livevol.

For example, implied volatility for the next 30 days for Citi fell 2.2 percent to an annual low of 29.36 percent while October's implied volatility rose about 7 percent to 33.81 percent. Even the implied volatility for the next 120 calendar days fell about 5 percent to an annual low of 31.35 percent, data from Livevol showed.

"Given the sudden departure of Citi's CEO, it seems that the share price may be more volatile in the next few days," said Ophir Gottlieb, managing director at Livevol in San Francisco. "Ultimately, the news has not been perceived as risky in the long run."

Some strategists are betting the shares will rise significantly in the next few months by snapping up January 2013 upside $41 and $44 strike calls, according to Interactive Brokers Group options analyst Caitlin Duffy in a note regarding Tuesday morning options activity.

The January 2014 upside $45 strike calls were also active, trading more than 10,000 times, with 98 percent of the activity on the ask price, indicating they were bought.

Pandit took the CEO job in December 2007, and steered the bank through the financial crisis.

TD Ameritrade's Kinahan said Corbat's promotion was a "signal to the Street that Citigroup's financial and mortgage crisis is over and so there is new leadership for a new direction."

Share volume on Citigroup was greater than average, as just over 128 million shares traded on Tuesday, or about 3.7 times its daily average over the last 50 days.

"Some investors think this is a big positive as the new management will concentrate on enhancing shareholder value," said William Lefkowitz, options strategist at New York-based brokerage vFinance Investments.

"But other traders believe that Citigroup is going through a state of confusion and this can only be perceived as a negative for the shares," Lefkowitz said.

(Reporting By Doris Frankel; Editing by Tim Dobbyn)