ATHENS--Greece's largest lenders are working to raise money to cover massive holes left behind by the country's debt restructuring, with one bank admitting Monday it has given up the chase and will turn exclusively to the government for help, and another saying it has enough funds to prevent a complete loss of management control to the state.

The country's four big lenders--National Bank of Greece SA (ETE.AT, NBG), Eurobank Ergasias SA (EGFEY, EUROB.AT), Alpha Bank SA (ALPHA.AT) and Piraeus Bank SA (TPEIR.AT), who, combined, control more than four-fifths of Greek banking assets--need to raise some 27.5 billion euros ($35.9 billion) after they were wiped out by the country's EUR200 billion debt restructuring last year.

In a day of mixed news for the sector, Eurobank admitted to being the first domestic bank to fall under state control, dropping plans to raise money from investors that would have secured management control of the lender.

Eurobank said its board decided Greece's bank rescue fund, the Hellenic Financial Stability Fund (HFSF), will fully cover a EUR5.8 billion rights issue and it could be recapitalized as early as next week.

"As one of the four systemic banks, Eurobank intends to actively engage in the strategic restructuring of the Greek banking system through the acquisition of smaller nonsystemic banks," it said.

The news comes after Greece halted earlier this month Eurobank's merger with National Bank of Greece, at a time of fears by the country's international lenders that the combined entity could become too big to be bailed out by the government. A Eurobank official said uncertainty over whether authorities would finally give the go-ahead for the merger hurt its chances of raising capital from investors.

As part of Greece's latest EUR173 billion bailout by its euro-zone peers and the International Monetary Fund, EUR50 billion has been set aside to recapitalize the country's four big banks. Under the terms of the plan, the banks must secure 10% of their capital needs from the private sector to maintain management autonomy and retain their private character.

Greece's bank-rescue fund will underwrite the balance but will have only restricted management rights if its share is less than 90%.

Piraeus Bank, however, had positive news--with the lender saying it has enough money to meet the 10% threshold after it agreed to purchase the Greek unit of Portuguese lender Banco Comercial Portugues SA (BPCGY, BCP.LB). The news sent Piraeus Bank shares 16% higher on the Athens bourse.

BCP will offload its Greek unit Millennium Bank by selling it for EUR1 million to Piraeus Bank and will invest EUR400 million in the Greek lender's upcoming rights issue, the two companies said in separate statements Monday. In addition, BCP will recapitalize its Greek unit before the sale closes by EUR400 million, the Portuguese bank said. About EUR139 million of that has already been injected.

"We are confident that we can achieve an even higher participation of private investors, in this landmark rights issue of Piraeus Bank," said Michalis Sallas, chairman of Piraeus Bank.

The Greek banking stocks index rose 18% on hopes the other two lenders--NBG and Alpha Bank-will be able to follow suit and keep control of management. In Lisbon, BCP shares trimmed gains of more than 4% to end up 2.1%, with investors cheered by news of the deal. Its Greek unit has long been a drag on the results of the Portuguese bank, which is also struggling with a recession at home.

The Portuguese bank, which last year received government help to improve its capital ratios, has been losing money in Greece due to the continuing economic problems in the country. With the transaction, BCP will lower its risk-weighted assets by about EUR4 billion, in turn raising its capital ratios. As of December, the bank's core tier 1 ratio was 9.8%.

Write to Stelios Bouras at Stelios.Bouras@dowjones.com and Patricia Kowsmann at Patricia.Kowsmann@wsj.com

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