EP Global Commerce already held a stake of nearly 11% in Metro. The offer price of 16 euros for each ordinary share and 13.80 euros for each preferred share represents a 34.5% premium to when EP Global Commerce made its initial investment in August.

The firm, co-owned by Czech investor Daniel Kretinsky and Slovak partner Patrik Tkac, said the offer was a "a compelling value and a unique opportunity" for shareholders given the difficult market and challenges facing Metro.

Metro said in a statement that it would study the offer, but advised its shareholders not to sell to the bidders for now.

Once a sprawling retail conglomerate, Metro has in recent years been restructuring to focus on its core cash-and-carry business, selling off the Kaufhof department stores and then splitting from consumer electronics group Ceconomy.

It still operates in 26 countries with 771 stores and 150,000 employees, but it is trying to offload its loss-making Real hypermarkets chain, as well as its operations in China.

The Czech and Slovak bidders signalled that further changes were needed at Metro, though they said they would not close stores in Germany and its core markets, or cut jobs substantially.

"Metro needs to regain the capability to swiftly react," they said, adding that otherwise, it "would be exposed to significant risks due to stagnant or declining results."

EP Global Commerce, which already held a 10.91% stake in Metro, made the full takeover offer after it agreed with investment firm Haniel to buy its 15.2% stake.

It also said it would exercise a call option for a stake of 5.4% held by an affiliate of Ceconomy.

(Reporting by Tom Sims and Matthias Inverardi in Frankfurt; editing by Matthew Lewis and G Crosse)