"The board of the ... CMVM has decided, under article 214 and part b) of nº 2 of article 213 of the Securities Code, the suspension of trading in shares in Banco BPI, S.A., until the release of relevant information about the issuer," the statement says.

There has been speculation in recent weeks about changes in the shareholder structure of BPI.

On Tuesday media reports suggested that Spain's Caixabank aims to acquire the 21% of the shares that are owned by Angolan investor Isabel dos Santos.

If such a deal went through the Spanish bank would increase its holding to some 44.1% and might bid for the rest.

Dos Santos, the daughter of Angola's long-serving president, José Eduardo dos Santos, is BPI's second-largest shareholder after Caixabank and last year fended off a takeover bid for BPI by the Spanish institution. She is seen as having little or no chance of gaining control herself.