SKYNEWS:(Source by BBC)Spain's main share index fell more than 2% before recovering, while shares in London fell by as much as 1%.
Confidence in European banks was undermined by ratings agency Moody's, which cut the credit ratings of 16 Spanish banks late on Thursday.
It also cut the debt rating on Santander UK, a subsidiary of the Spanish banking giant.
However, shares in Santander reversed early losses to trade 3% higher, and Bankia shares jumped 9% following Thursday's 14% slump.
Moody's said there were several reasons behind the downgrade, including Spain's slide back into recession, the financial challenges facing the Spanish government and bad loans in the property industry.
But Moody's also recognised that banks had made progress in improving their financial situation, and noted the European Central Bank was providing support.
In response to worries over Spain some investors moved money into German bonds, which are seen as low-risk investments. That drove the yield on 10-year German bonds down to 1.399% on Friday, a record low.
Negative messages In Asia stock markets registered heavy losses. Tokyo's Nikkei average fell 3%, the biggest one day fall since last August.
Asian markets were also hit by losses in New York, where the Dow Jones closed more than 1% lower.
Investors were discouraged by two weak reports on the US economy.
"There is no resolution to the [European] problem yet, and we also we had very disappointing US data, so overall, it's negative and further denting market sentiment," said Frances Cheung, a senior strategist, at Credit Agricole CIB in Hong Kong.
In Asia, banking shares were hurt after the chief executive of ANZ said volatile market conditions meant that Australian banks were not lending to each other.
The wholesale lending markets are an important source of funds for banks.
"Right now, markets are closed again, and this is what happens in this sort of situation," said ANZ chief executive Mike Smith.