Stress in the financial sector triggered by worries over global growth and the impact of negative interest rates drove European share prices to their lowest in 16 months on Monday and sent the cost of insuring bank debt soaring.Concern over the health of the sector, which has prompted comparisons with the early days of the global financial crisis in 2008, pushed borrowing costs in the euro zone's most indebted countries higher and sent investors to the relative safety of ultra-low-risk government debt.The gloomy mood in stock markets looked likely to carry over into U.S. trading hours, with index futures indicating Wall Street would open lower . Some U.S. bank shares traded sharply lower in Frankfurt. "The fundamental picture is clearly softening," said Owen Callan, senior analyst at Cantor Fitzgerald. "People are worried about the global economy and particularly now we are beginning to look at the banks.""You are seeing more and more people saying: is this 2008 again? Maybe not quite as severe, but do we need to be worrying about the banking sector and risk assets on a bigger level?"The STOXX Europe 600 banking index fell 3.7 percent, underpeforming the broader market, which was down 2.7 percent and the pan-European FTSEurofirst 300 index , down 2.6 percent.Shares in Deutsche Bank, Commerzbank, Credit Suisse, HSBC and BNP Paribas fell between 3.5 percent and 6.7 percent. "Concerns are increasing that in a climate of negative interest rates and prolonged dovish monetary policy, banks' profitability will be squeezed," Jaisal Pastakia, investment manager at Heartwood Investment Management, said."A high level of unprofitable loans on banks' balance sheets impacts the broader economy by stifling both domestic demand and bank lending growth," Pastakia added. The cost of insuring the subordinated debt of European financial firms rose 12 percent on Monday to its highest since April 2013, Markit's iTraxx index showed. A similar index for financials' senior debt hit its highest since October 2013. Both indices are up around 40 percent in the past week.Shares in U.S. banks Citigroup and JPMorgan trading in Frankfurt were down 3.5 and 3.7 percent respectively, albeit in very low volume.Worries over the banks pushed up borrowing costs in Portugal, Spain and Italy - three countries that were at the heart of the euro zone sovereign debt crisis.Yields on Portugal's 10-year debt rose 21 basis points to 3.14 percent, their highest since July 2015.At the same time, German 10-year yields, the euro zone benchmark, fell more than 6 bps to 0.25 percent and two-year yields hit a record low of -0.506 percent.Ten-year U.S. Treasury yields fell 5.5 bps to 1.79 percent.