Italian investment firm Exor S.p.A. on Tuesday said it is raising its all-cash offer to acquire Pembroke, Bermuda, reinsurer PartnerRe Ltd. to $137.50 per share in cash from $130 per share, valuing PartnerRe at $6.8 billion.

Exor said in a statement that its offer of $137.50 per share “represents a 10% premium to the implied value of $125.17 per PartnerRe share under the revised amalgamation agreement between PartnerRe and Axis Capital Holdings Ltd.,” with whom Exor is locked in a battle for control of PartnerRe, “based on the Axis closing price on May 5, 2015, the last day prior to published reports of takeover interest in Axis, if its transaction with PartnerRe fails.”

Analysts had previously said that a higher bid of between $135 per share and $140 per share could be justified based on PartnerRe's reserves, believed to robust.

Exor also said that it has now invested $572 million in PartnerRe, representing 9.32% of the total outstanding common shares and making Exor PartnerRe's largest shareholder

Exor's move comes after Axis, which had plans to merge with PartnerRe, improved its initial merger proposal with the addition of a one-time special dividend of $11.50 per share.

Exor taking more aggressive stance

Axis and PartnerRe's original merger agreement was thrown into doubt with Exor's initial $130-per-share offer. When Axis declared the special dividend, both companies reiterated their commitment to the merger and said they had made significant integration progress.

“Despite rejecting Exor's initial proposal, PartnerRe's board effectively acknowledged the superiority of Exor's transaction by seeking a revised agreement with Axis (albeit on terms that continue to be inferior). Exor's $137.50-per-share all-cash binding offer widens the gap further and unequivocally provides an opportunity for superior value to shareholders,” Exor said in its statement.

Exor also said it is preparing to take its offer to PartnerRe's shareholders.

“Exor's binding offer clearly delivers superior and certain value for PartnerRe shareholders, and provides a more attractive outcome for the Company's employees and clients … we believe PartnerRe shareholders deserve the opportunity to choose our offer and, in order to do so, we urge them to vote against the inferior Axis transaction,” John Elkann, chairman and CEO of Exor, said in the statement.