(Adds details, analyst comments, updates share price)
By Ross Kerber and Tim McLaughlin
BOSTON, May 1 (Reuters) - The French parent of asset manager AllianceBernstein fired its longtime leader Peter Kraus, replacing him with a new chief executive and and new chairman, and overhauled the firm's board, according to a filing Monday that offered little explanation for the unexpected changes.
New York-based AllianceBernstein, which is 64 percent owned by France's AXA SA, named JPMorgan Asset Management executive Seth Bernstein as its new CEO and Robert Zoellick, previously president of the World Bank and a former Goldman Sachs executive, as chairman.
Kraus, who held the CEO and chairman titles since 2008, was "terminated" from his job as CEO, according to a securities filing.
AllianceBernstein, with $497.9 billion in assets under management at the end of March, gave no hint of changes in the works when it reported earnings on Thursday.
The filing also said that on Friday an AXA unit removed nine directors from the AllianceBernstein board, including Kraus, and the next day named replacements to fill most of the seats on the board which now has eight members.
A spokesman declined to comment on the reason for the changes. Representatives at AXA's Paris headquarters were not available to comment on the moves, which came eight months after Thomas Buberl took over as CEO of the giant French insurer.
AllianceBernstein shares fell 3.28 percent to $22.15.
Kraus, himself a Goldman Sachs veteran, took over as CEO and chairman in 2008, just as the financial crisis gripped Wall Street. He helped shepherd AllianceBernstein in the difficult years that followed, but it has not fully recovered.
AllianceBernstein's assets of $497.9 billion are well below the $800.4 billion it managed at the end of 2007. It is now dwarfed by companies with stronger lineups of passive investment products such as BlackRock Inc, which ran $5.4 trillion at the end of March.
On a conference call on Monday morning, AXA Board Chairman Denis Duverne thanked Kraus for his service as CEO.
"After eight years, we decided it was time to put in new leadership," Duverne said during the call. Analysts pushed for more detail on the abrupt changes at the top, but Duverne declined to say what, if anything, was lacking during Kraus' watch.
In a note to investors Jefferies analysts wrote the shake-up "produces more questions than answers" and that the new management structure may signal a closer alignment between AllianceBernstein and AXA, where six board members now have ties.
AXA executives cited a changed industry since Kraus came in, the Jefferies analysts wrote, implying that "AXA disagreed with the strategy being pursued by the previous management team and did not want to wait until the end of Peter's contract to make changes as industry headwinds are only accelerating."
Citigroup William Katz wrote however the change may not reflect strategic or financial issues because management had little other news, and that "potentially personal conflict drove the sudden change."
Kraus had given no indication of changes ahead. On a conference call after the company's earnings last week, he said: "We've focused for years on rebuilding our presence and regaining relevance with retail clients and are finally where we need to be."
Kraus has entered into a "cooperation agreement" with AllianceBernstein, under which he is entitled to termination benefits and salary, according to the filing. According to the filing AXA has agreed to buy from Kraus stock units worth $99.3 million. He may also receive restricted units in the future, the filing states.
Reporting by Ross Kerber and Tim McLaughlin in Boston. Additional reporting by Maya Nikolaeva in Paris.; Editing by Bill Rigby and Andrew Hay