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Shares of Aflac Inc.  (AFL) climbed 5.06% to $45.07 Thursday on news that Japan Post Holdings Co. reportedly was planning to invest about $2.6 billion in the Columbus, Georgia-based insurance company. 

Japan Post, a conglomerate that includes postal delivery, banking and insurance services, plans to initially acquire a 7% to 8% stake in Aflac for about 300 billion yen, or about $2.6 billion, according to Reuters, citing a person familiar with the matter.

Under the deal, Japan Post can increase its stake to a maximum 20% in four years, the Reuters story said, noting that Aflac's current largest shareholder is Vanguard Group Inc., which has an 8.77% stake.

Aflac said in a statement it was engaged in discussions with Japan Post regarding a potential minority investment but "the discussions do not involve Aflac Incorporated or any of its subsidiaries becoming a member of the Japan Post Group."

"No assurance can be given that any transaction will occur or agreement will be reached," the statement said. "Aflac Incorporated is not otherwise in a position to comment on the terms, timing or form of any transaction."

Aflac said that it doesn't intend to make any further press releases or announcements regarding about the matter "unless a definitive agreement has been reached or discussions have terminated."

In 2013 Aflac signed an agreement with Japan Post allowing Aflac to sell its cancer insurance at Japan Post's offices across Japan.