PARIS, May 7 (Reuters) - The Euro STOXX 50 volatility index , Europe's main barometer of anxiety known as VSTOXX index, surged 6 percent to a four-month high at 31 on Monday, as investors' risk aversion rises following elections in Greece and France.

The higher the volatility index, based on sell- and buy-options on the Euro STOXX 50 stocks, the lower investors' appetite for risky assets.

Investors were rattled by results of elections in France and Greece showing public discontent with austerity measures and fuelling worries over the euro zone's ability to fix its debt crisis.