(Reuters) - Sanofi's board ousted its chief executive of six years at a special meeting on Wednesday, two days after it emerged he had fallen out with the French drugmaker's chairman, wiping more billions off its market value.

The board said Sanofi would continue the strategy of international expansion it had pursued under Chris Viehbacher, blaming his dismissal on poor relations between the CEO and the board.

It said Chairman Serge Weinberg would take on the CEO role until a replacement for the ousted German-Canadian Viehbacher was found. Weinberg said on a conference call that there had already been contacts with potential candidates.

"The board of directors held a meeting Wednesday, October 29 at 8am and decided unanimously to remove Christopher A. Viehbacher as chief executive officer of Sanofi," the board said in a statement.

"As a consequence, Christopher A. Viehbacher resigned as a director of Sanofi."

Viehbacher had been unable to say on Tuesday during a quarterly results conference call whether he had the support of his board after the chairman declined to clarify his future during a meeting the previous day.

In the results, the company warned its key diabetes business would probably not grow next year.

Shares in Sanofi were down more than 4 percent in early trading on Wednesday, contributing to a three-day drop of close to 16 percent. The stock is down 20 percent this month.

Sanofi's shares fell more than 10 percent on Tuesday alone, their biggest drop in 17 years and wiping off 13 billion euros of market value in two days.

Uncertainty over Viehbacher's role first surfaced on Monday with the publication of a Sept. 4 letter he sent to the board asking for clarity about his position.

Several sources close to Sanofi's board told Reuters this week of an increasingly frosty relationship between Viehbacher and Weinberg, Sanofi's chairman since 2010.

Sanofi's first non-French boss, he took his job in late 2008. He has transformed a very French drug company by making it more international, winning the praise of many analysts and investors but raising some hackles in Paris and directly butting heads with some board members over the past several months.