By Alexandra Edinger, Ulrike Dauer and Eyk Henning

FRANKFURT--A co-owner of German primary insurer Provinzial Nordwest Holding AG said Friday it isn't planning to sell its 40% stake in the German insurer and that a sale would need the approval of all shareholders.

The statement by the regional authority, or Landschaftsverband, of Westphalia-Lippe, follows a report by Financial Times Deutschland that Allianz SE (ALV.XE) plans to buy Provinzial, which is owned by German public-sector savings banks.

The newspaper, without citing sources, said Allianz is offering 2.25 billion euros ($2.91 billion), equivalent to Provinzial's book value, and that Chief Executive Michael Diekmann recently met the insurer's three owners to discuss the offer.

The Landschaftsverband owns 40% of Provinzial , the savings banks in Westphalia-Lippe own another 40%, the savings banks in Schleswig-Holstein own 18%, and the eastern German savings banks own the remaining 2%.

"In the past, we've repeatedly received offers for the economically sound company," said Wolfgang Kirsch, who heads the Landschaftsverband, adding that the insurer "can only be sold with the approval of all shareholders."

Representatives for Allianz and the savings banks in Westphalia-Lippe and eastern Germany declined to comment.

A spokeswoman for Provinzial also declined to comment and referred to the statement by the co-owner. The savings banks in Schleswig-Holstein weren't immediately available to comment.

According to its annual report, Provinzial had gross premium revenues of EUR3.04 billion in 2011 and booked a net profit of EUR116.2 million. It employs 2,960 people.

Write to Alexandra Edinger at alexandra.edinger@wsj.com, Ulrike Dauer at ulrike.dauer@wsj.com, and Eyk Henning a eyk.henning@wsj.com

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