Polling stations across crisis-hit Venezuela opened Sunday for a presidential election in which President Nicolas Maduro is expected to be easily reelected.

Maduro, the political heir to the late leftist firebrand Hugo Chavez, is expected to defeat Henri Falcon, a former army officer who failed to gain the endorsement of the main opposition leaders, and evangelical candidate Javier Bertucci.

Polls opened at 6 am (1000 GMT) and are scheduled to close at 6 pm (2200 GMT).

About 20.5 million people were eligible to vote, but many analysts expected a low turnout after the opposition alliance Democratic Unity Roundtable (MUD) called on voters to boycott the poll.

MUD sees the elections as a "farce" only aimed at legitimizing the continuation of Maduro's rule.

The president's electoral campaign had the support of the state apparatus, and suspicion is rife that the pro-government electoral authority could rig the results.

The United States, 14 Latin American countries and the European Union have denounced the elections as undemocratic.

The U.S. on Friday added top ruling party official Diosdado Cabello and three other Venezuelans to its list of individuals targeted in Maduro-related sanctions.

Falcon has proposed substituting Venezuela's almost worthless currency, the bolivar, with the U.S. dollar to stem hyperinflation in the country, which the International Monetary Fund expects to reach 13,000 per cent this year.

The economy of the oil-producing country will contract by 15 percent in 2018, according to the IMF.

Shortages of food, medicines and basic goods have sent hundreds of thousands of Venezuelans fleeing to neighboring countries.

In addition to electing a president, Venezuelans will also vote for members of state and municipal legislative councils. First results were expected late Sunday.