Allianz chief executive Michael Diekmann told a press conference in Munich, southern Germany, that uncertainty caused by new capital requirements for European insurers made it hard to give a more precise outlook.
"For the 2011 exercise, we foresee an operationg profit of €8 billion, give or take €500 million owing to uncertainties," Diekmann said.
Shares in the biggest European insurer were then hammered in midday trading on the Frankfurt stock exchange.
The Allianz boss underscored optimism for the full-year but warned that a new set of EU capital requirements known as Solvency II needed to be clarified because they might entail risks for some of Allianz's activities.
"Owing to uncertainties over Solvency II we cannot make any large acquisitions," Diekmann noted.
The new regime is to take effect in 2013, but some details must still be finalised and an insurer might have to raise its capital significantly, which would undermine earnings and make some activities unattractive, he explained.
Allianz finance director Paul Achleitner said the uncertainty could also affect Allianz's investments in financial markets.
For 2010, the group reported a 17 percent jump in operating profit to €8.2 billion, exceeding its own target and analyst forecasts thanks in part to €500 million in exceptional items, including positive effects from foreign exchange rates.
Allianz's net profit leapt by 20.1 percent to €5.05 billion. "All our divisions contributed to the result," Diekmann commented.
Revenues gained 9.3 percent to a record high of €106.5 billion, and Allianz directors will propose a dividend of €4.50 per share, up from €4.10 in 2009.
Investors apparently had hoped for more and the group's share price plunged in midday Frankfurt trading, showing a loss of 3.01 percent to €101.45 while the DAX index of German blue-chips was 1.13 percent lower overall.