Unizo Holdings Co.'s latest takeover offer is seen raising the bar for Blackstone Group Inc., which has been the most persistent bidder in the war for the Japanese real estate operator.

Unizo backed a takeover offer made by its employees in partnership with Lone Star Group worth ¥174.4 billion ($1.6 billion), saying in a statement Sunday that the offer price of ¥5,100 per common share is above proposals made by other bidders. The stock rose as much as 6.1 percent to ¥5,200 in Tokyo on Monday.

Unizo has been caught in a rare battle among global investing behemoths since a travel agency operator launched a surprise tender offer in July. Fortress Investment Group and a number of other investment firms joined the fray before Blackstone came in with an offer of ¥5,000 per share. Unizo has withheld support for that offer as it became clear that management was getting cold feet about an outright sale.