Bain and Cinven last month won the majority of Stada shares with a sweetened 5.24 billion euro (£4.8 billion) bid including debt, offering 66.25 euros per share in the largest private-equity funded takeover of a German listed company.

They had acceptances for close to 64 percent of the shares, but under the German takeover code need the backing of more than 75 percent of shareholders to tap into Stada's cashflow via a so-called domination and profit and loss transfer agreement.

Elliott said on Thursday, however, it wanted at least 74.40 euros per share for its stake, which most recently stood at 13.3 percent, or 15.2 percent when taking stock options into account.

If a 74.40 euros a share offer were to secure Bain and Cinven all remaining shares they have not already been offered, the total price tag for Stada including debt would rise by about 180 million euros to 5.42 billion euros.

Bain and Cinven said in a statement late on Sunday that while they were "convinced that the fair value of Stada shares is below the price required by Elliott" they would propose offering minority shareholders 74.40 euros in cash per share.

"Bain Capital and Cinven firmly believe that Stada, its business and its stakeholders substantially benefit from certainty on the success of a DPLTA (profit and loss agreement)," they said.

The shares had jumped 3.2 percent to 82.05 euros by 0740 GMT, with buyers betting that some minority investors might hold out for an even higher offer.

Stada shares were trading at 62 to 64 euros in the first week of July when first reports emerged that Elliott was building a stake in Stada.

Germany-based officials representing Elliott could not immediately be reached for comment.

(Reporting by Ludwig Burger, Maria Sheahan and Patricia Weiss; Editing by Stephen Coates and Mark Potter)