Central banks intensified warnings that Europe's failure to tame its debt crisis threatens to roil the world's financial markets and economy as Greece's election in two days looms as the next flashpoint for investors.

Monetary policy makers from the U.K. to Japan and Canada sounded the alert about potential fallout from the single currency bloc's troubles. They spoke as Group of 20 leaders prepare to meet in Mexico next week amid the weakest international economy since the 2009 recession.

A victory by Syriza, the party that promises to renege on Greece's end of the bailout deal, could speed the nation's exit from the euro. Absent a quick fix from divided European governments, central bankers may have to engage in fresh crisis-fighting of their own to ensure markets operate and their economies grow if the election jolts investors. Spain's 10-year bond yield vaulted to 7 percent yesterday in a fresh sign of the stress that has plagued the region for two years.