* FTSEurofirst 300 index down 2.5 percent in late session
* Spain's IBEX down 5.6 pct, Milan's MIB down 4.6 pct
* For up-to-the minute market news, click on [
] By Joanne FrearsonLONDON, May 14 (Reuters) - European shares extended sharp losses late on Friday, led by banks, on worries that tough new fiscal austerity measures in the euro-zone's weaker economies will slow economic growth.
By 1425 GMT, the pan-European FTSEurofirst 300 <
> index of top shares was down 2.5 percent at 1,024.02 points having earlier fallen as low as 1,016.95.But the index is still on track to record a weekly gain of about 5.7 percent after Monday's sharp rally triggered by the $1 trillion emergency rescue package to stabilise the euro-zone.
Banks took a beating on Friday, withthe STOXX Europe 600 banking index <.SX7P> down 4.7 percent. Spanish banks Banco Santander <SAN.MC> and BBVA <BBVA.MC> fell 7.4 and 6.1 percent respectively.
"Above all it is lack of confidence in Spain which is hitting the Spanish market and big banks, along with builders, have been hurt most for their hefty debt piles," a Madrid-based trader said.
Spanish builder Sacyr <SVO.MC> fell 6.1 percent and energy, water and construction group Acciona <ANA.MC> shed 6.2 percent.
French banks Credit Agricole <CAGR.PA> and Societe Generale <SOGN.PA>, both significantly exposed to Southern Europe, lost 5.5 percent and 7.4 percent respectively.
The euro <EUR=> was also hit hard, dropping to a fresh 18-month low against the U.S. dollar.
Over the past few months, European stocks have been hammered by escalating fears over the risk of Greek debt problems spreading to other countries in the region, strongly underperforming U.S. peers.
So far this year, Greece's ATG index <
> has plummeted 25 percent, Spain's IBEX < > is down 21 percent, Portugal's PSI 20 < > down 17 percent, Italy's MIB <.FTMIB> down 14 percent and France's CAC 40 < > down 8.4 percent.Wall Street's S&P 500 <.SPX> is up 2.3 percent year-to-date.
Greece, Portugal, Ireland and Spain together account for about 18 percent of euro zone gross domestic product (GDP).
"In the coming months, the market will be hesitating between sovereign-debt fears and economic-growth fears for the euro zone," said Claire Chaves d'Oliveira, head of equity management at Groupama AM in Paris.
"We can't have it both: an economic recovery and reducing the debt at the same."
A Reuters poll of economists in April gave a median forecast for euro zone GDP growth of just 1.0 percent this year and 1.5 percent next year, compared to 3.0 percent and 2.9 percent for the United States. [
](Additional reporting by Rodrigo de Miguel in Madrid; Blaise Robinson and Juliette Rouillon in Paris; editing by Quentin Webb)