* FTSEurofirst 300 down 0.5 percent
* Global worries hitting corporate results
* Zurich Insurance falls after Q3 profit miss
By David Brett
LONDON, Nov 15 (Reuters) - European shares extended losses on Thursday as the rising threat to global growth from the United States and Europe prompted investors to reduce their exposure to risky assets.
A sharp sell-off in shares on Wall Street also made investors nervous and by 0842 GMT, the FTSEurofirst 300 was down 4.84 points, or 0.4 percent at 1,083.59, having fallen 1 percent on Wednesday. The euro zone blue chip index fell 0.4 percent to 2,463.65.
Shares fell as U.S. politicians readied themselves for a tough battle over the 'fiscal cliff' of some $600 billion in automatic tax hikes and spending cuts, and ahead of data which is expected to show the euro zone has slipped back into recession.
"The global economy faces some severe headwinds. Against that backdrop we see short-term de-risking of portfolios," Abi Oladimeji, head of investment strategy at Thomas Miller Investment, said.
He said there was a convincing case for reducing equity allocations given pressures on the global economy from the euro zone and the United States in particular, as well as overly bullish investor sentiment over the summer.
Riskier basic resources stocks - demand for which is acutely tied to the performance of the broader economy - fell 1.1 percent in early trade as investors sought safer havens.
Insurers, which have rallied over the last three months as central banks stepped in to shore up the global economy, also fell 1 percent.
Zurich Insurance Group shed 3.4 percent after missing third-quarter profit expectations, while British life insurer Resolution was 4.7 percent lower after being hit by rising IT costs.
Among companies in Europe that have reported third-quarter earnings so far, 43 percent have missed expectations, according to Thomson Reuters Starmine data.
Reflecting concerns over the economic outlook, analysts have cut their fourth-quarter earnings estimates for European firms by an average of 3.6 percent.
Early falls in European share markets followed a sharp decline in U.S. stockmarkets.
Traders cited concerns that the sell-off on Wall Street was supported by solid volumes. It also broke technicals including the 1,360 level, the short-term trendline on the S&P 500, and marked a convincing break below the 200-day moving average, which had not been achieved since early June.
In Europe, Philippe Delabarre, technical analyst at Trading Central, said EXTOXX50 December 2012 futures were showing signs of downward pressure too.
"A bearish continuation pattern in the consolidation channel is confirmed. Therefore, a measured move down is ongoing. Furthermore, the Relative Strength indicator is evolving below its neutrality area (50) without being oversold (30)," he said.