VENEZUELAN officials declared socialist leader Nicolas Maduro the easy winner of the presidential election.

But his leading challenger questioned the legitimacy of a vote marred by irregularities and called for a new ballot to prevent a brewing social crisis from exploding.

The National Election Council announced that with almost 93% of polling stations reporting, Maduro had won nearly 68% of the votes, beating nearest challenger Henri Falcon by almost 40 points.

The disputed victory is likely to heighten international pressure on Maduro, as voter turnout was the lowest in a presidential race since the start of Venezuela’s leftist revolution two decades ago.

Even as voting was taking place on Sunday, a senior state department official warned that the US might press ahead on threats of imposing crippling oil sanctions on the nation that sits atop the world’s largest crude reserves.

The election “without any doubt lacks legitimacy and we categorically refuse to recognise this process”, Falcon told supporters before the results were announced.

He was joined in his call for a new election by third-place finisher Javier Bertucci, who got around 11% of the vote.

But he said that in the event of a new vote, Maduro should do the dignified thing and refuse to run. If Maduro pressed forward, he said, Venezuela would explode from a social crisis marked by widespread food shortages and hyperinflation before his new term started next January.

Both of Maduro’s opponents accused authorities of turning a blind eye to a slew of blatant violations, including the pitching of red tents just steps away from voting centres where ruling party activists scanned on cellphones government-issued “Fatherland Cards”. Many voters said they hoped it would bring them a cash bonus or even a free apartment.

Under Venezuela’s electoral law, any political activity must take place at least 200m from voting centres.

Falcon, a one-time acolyte of the late President Hugo Chavez, said his campaign found “red points” at 86% of polling sites nationwide. He called them a “pressure mechanism, an element of political and social blackmail” directed at the poor.