Spain's stock market regulator, the CNMV, said on Thursday it banned short selling on financial stocks for 15 days from August 11 and added it would extend the period if necessary.

The situation of extreme volatility in European stock markets, especially for shares of financial entities, is clearly affecting the stability of the markets and can disrupt their ordered functioning, it said in statement.

The groups on which short trading is banned include Santander , BBVA , Sabadell , Bankinter , Banco Popular

, Banca Civica , Banco de Valencia, Banesto , Banco Pastor

, Bankia , Caixabank , CAM , Grupo Catalana de Occidente, Mapfre, BME and Renta 4.

The announcement from the regulator came shortly after the European Union's financial market regulator ESMA said Belgium, France, Italy and Spain would pass new bans on short selling or short positions after heavy volatility on EU stock markets.

(Reporting by Paul Day; editing by Andre Grenon)