Madrid  - The shares of top Spanish banks plunged Monday following US investment bank Lehman Brothers announcing it would file for bankruptcy protection.

The country's two biggest banks, Santander and Banco Bilbao Vizcaya Argentaria (BBVA), were down 3.44 and 3.53 per cent respectively 40 minutes after trading started on the Madrid stock exchange.

Banco Popular dropped by 3.33 per cent, Banesto 3.19 per cent, Sabadell 3.32 per cent and Bankinter 2.07 per cent in the Ibex-35 index. (dpa)