Spanish bank Bankia on Thursday sold its 12.09 stake in International Airlines Group, which was formed by the merger of Spain's Iberia and British Airways, to institutional investors for 675 million euros ($880 million).

In a regulatory filing, the nationalized lender estimated it made a capital gain of 167 million euros on the sale.

Bankia, which had been the largest Spanish investor in IAG, placed 224.25 million shares at a price of 3.01 euros per share, or a 2.96 discount to Wednesday's closing price.

The Spanish lender had inherited the IAG stake from Caja Madrid, one of seven regional Spanish banks that merged to form Bankia in 2010. Caja Madrid had been the largest shareholder in Iberia.

Under the restructuring plan for the nationalized bank that was approved by Spain's central bank and the European Commission, Bankia and its parent company, BFA, must divest non-strategic assets between 2012 and 2015.

Bankia, which has received public aid to overcome its financial woes, still owns shares of other companies, including a 5 percent stake in Spanish electric utility Iberdrola and 15 percent in Spanish insurance company Mapfre.

None of the institutional investors who bought Bankia's IAG stake acquired more than 1 percent of the airline group's capital, and therefore are not required to report their purchase to Spain's CNMV stock-market regulator.

The list of buyers included a sizable portion of U.S. and British investment funds but also others based in Spain. EFE