Santander of Spain, regarded as one of the strongest banks in Europe and the biggest in the eurozone by market capitalisation, unsettled the markets on Monday with the surprise announcement of a deeply discounted €7.2bn ($9.2bn) rights issue to bolster its capital ratios.

Only weeks ago, senior executives of the acquisitive bank were boasting of their ability to buy other banks weakened by the global financial crisis and insisting that Santander itself did not urgently need more capital.