Nicolás Maduro, Venezuela’s long-ruling authoritarian president, issued a stark warning to the opposition ahead of Sunday’s election, labelling them fascists, cowards and US puppets and telling them not to question what he claimed would be his overwhelming victory.

Tensions have risen sharply in recent weeks as opinion polls have forecast the main opposition candidate, 74-year-old retired diplomat Edmundo González, could beat Maduro by a margin of 20 to 30 percentage points, an outcome that would spell the end of Venezuela’s Cuban-backed revolutionary socialist government after a quarter of a century in power.

In a fiery final campaign speech lasting more than an hour and addressed to an audience of tens of thousands of flag-waving workers bussed in to Caracas, the capital, Maduro hailed his success in defeating US sanctions on the economy, spoke of his devotion to Jesus Christ and revolutionary socialism and vowed not to tolerate opposition accusations of foul play.