ATHENS (Reuters) - Greece's fourth-biggest lender Alpha Bank (>> Alpha Bank S.A.) said on Monday that about 21 percent of its 10,000 employees took up a voluntary redundancy offer the bank launched last month as part of moves to cut costs.

Alpha had aimed to cut about 15 to 20 percent of its workforce to squeeze its cost base under a restructuring plan approved by the EU Commission.

The scheme expired on Sept. 30. The bank said about 2,200 employees participated in the plan.

All four of Greece's top banks have been restructuring. Alpha's bigger rivals National Bank (>> National Bank of Greece), Piraeus (>> Piraeus Bank SA) and Eurobank (>> Eurobank Ergasias SA) completed similar job cutting schemes last year.

Piraeus shed about 12 percent of its workforce via a voluntary redundancy scheme in September 2013, while more than 10 percent of Eurobank's staff departed through a voluntary scheme in November last year.

In December, more than 2,000 people signed up for a voluntary redundancy scheme at Greece's biggest lender, National Bank, which aimed to shed about 15 percent of its workforce to cut costs.

(Reporting by George Georgiopoulos; editing by Susan Thomas)