Bain Capital is launching an unexpected $4.3bn counterbid for IT company Fuji Soft, reigniting Japan’s most fiercely contested takeover battle of the year with a renewed challenge to rival private equity group KKR.

Bain Capital is increasing its offer for Fuji Soft Inc. with a bid that values the Japanese software company at $4.3 billion, extending a rare battle with KKR & Co. in the country’s booming buyout market.

U.S. private equity firm Bain Capital will raise its offer price for Japan's Fuji Soft by around 1.6%, it said on Wednesday, trumping a recently increased tender offer bid from rival KKR. Bain's increased offer price,

Bain Capital is increasing its offer for Japanese information technology company Fuji Soft Inc., people with knowledge of the matter said, prolonging a rare bidding war with KKR & Co. in the country’s booming buyout market.

KKR and Bain have been competing for Fuji Soft. KKR announced last month that it would offer 1 yen higher than Bain's earlier bid. Fuji Soft's board of directors unanimously expressed a supportive opinion of KKR's offer, recommending that shareholders tender their shares.

U.S. private equity firm Bain Capital is set to raise its offer price for Fuji Soft to 9,600 yen ($63.35) from 9,450 yen to counter KKR's tender offer bid, the Nikkei business daily reported on Wednesday.