Ammon News - BBC - Real Madrid and Barcelona are among seven Spanish clubs to be investigated over alleged illegal state aid.
The Spanish foreign ministry announced that the European Commission will also begin proceedings against Osasuna, Athletic Bilbao, Valencia and Elche.
Hercules, who play in the second tier, are also under investigation.
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"The government will fight to defend Spanish clubs because they're also part of the Spanish brand," said foreign minister Jose Manuel Garcia Margallo.
The proceedings could take months to conclude and will be officially announced on Wednesday added Margallo, who denied the clubs had broken EU rules.
He said Barcelona, Real Madrid, Osasuna and Athletic Bilbao are accused of contravening European Union rules because they are still owned by their members and had benefited from favourable tax treatment.
The Commission was also probing Real over their training facilities and Bilbao over aid they received for the construction of their new stadium, which opened this season, he added.
Valencia, Elche and Hercules were being investigated because of help the three clubs received from the regional government in the form of loans and bank guarantees.