At least five people were killed in renewed clashes between police and protesters in Venezuela, where a 48-hour strike called for by the opposition is taking place.

The Venezuela prosecutor's office said a 49-year-old man was killed during a protest in Carabobo state and a 16-year old died in El Paraiso, Caracas on Thursday.

That added to the previously announced deaths of a 23-year-old man and a 30-year-old man killed in western Merida state and a 16-year-old boy killed in the Caracas neighborhood of Petare during clashes on Wednesday.

The latest casualties bring to 108 the number of people killed in four months of violent protests against the government of President Nicolas Maduro, the AFP news agency said.

Maduro's opponents at home and abroad are attempting to pressure him into halting his plans to rewrite Venezuela's constitution with an election for a Constituent Assembly on July 30.

The opposition-led two-day strike is the latest effort to bring Venezuela to a standstill.

Highways were mostly empty, and businesses shuttered across the country as millions of people observed the protest.

Activists threw up roadblocks in many neighbourhoods to keep others from getting to work, but the protest soon turned violent.

The strike came as the United States announced sanctions on 13 senior Venezuelan officials.

The US Treasury Department issued the punishing measures, saying the "flawed" election process would undermine democracy.

A defiant Maduro hit back late on Wednesday, holding a campaign style rally where he presented some of those hit by US sanctions with replicas of a sword belonging to Latin American independence hero Simon Bolivar.

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"Congratulations for these imperialist sanctions," he said, before handing out the symbolic swords. "For us, it's a recognition of morality, loyalty to the nation, and civic honesty."

Maduro accuses the US of fomenting the unrest against him and his government, with the help of the conservative opposition.

'Constitutional fraud'

Venezuela is days away from starting the process of rewriting its constitution by electing members of a Constituent Assembly, which will override the current opposition-led legislature.

The opposition is boycotting Sunday's vote, saying election rules were rigged to guarantee Maduro a majority in the assembly.

Polling firm Datanalisis says some 70 percent of Venezuelans are opposed to the Constituent Assembly.

Opposition leader Leopoldo Lopez appealed to the military, which is fiercely loyal to the president, to withdraw its support from Maduro's plan, which he called a "constitutional fraud" aimed at eliminating democratic rule.

"We are on the brink of their trying to annihilate the republic that you swore to defend," Lopez said in a 15-minute video message. "I ask you not to be accomplices in the annihilation of the republic."

After the strike, the opposition has planned a demonstration for Friday billed as a "takeover of Caracas."

"It's the only way to show we are not with Maduro. They are few, but they have the weapons and the money," decorator Cletsi Xavier told Reuters news agency.

Meanwhile, Telesur, a television network sponsored by several Latin American governments including Venezuela, reported that thousands of Maduro supporters rallied across the country on Wednesday in support of the election.

In a Twitter post, Diosdado Cabello, the vice president of the ruling Socialist Party, said Venezuela remained "absolutely calm". He posted pictures of hundreds of red-clad government supporters at a rally in the state of Monagas.

Amor con amor se paga, en Monagas como en toda Venezuela #LaConstituyenteSiVa, Pueblo en la calle, mi corazón de Patriota con ustedes pic.twitter.com/87tXVUnZjI — Diosdado Cabello R (@dcabellor) July 26, 2017

US sanctions

US officials said the individual sanctions aimed to show Maduro that Washington would make good on a threat of "strong and swift economic actions" if he goes ahead with Sunday's vote.

Among those hit by US sanctions were Tibisay Lucena, the president of the national elections council; Simon Zerpa, the vice president of the state oil company PDVSA; and prominent former ministers Iris Varela and Elias Jaua.

In addition, penalties will apply to several members of Venezuela's National Guard, police and other security services.

The administration of US President Donald Trump spared Venezuela from broader sanctions against its vital oil industry, but such actions were still under consideration.

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Thirteen countries in the 35-member Organization of American States, a regional political bloc, have also urged Maduro to suspend the election.

Adding to Venezuela's isolation, a major Latin American airline, Avianca of Colombia, said it would stop flights to and from Venezuela in mid-August. It cited security concerns for the move.

Meanwhile, thousands of Venezuelans have fled the unrest this week, crossing the border into Colombia laden with heavy bags.

"The elections are on Sunday, and we really don't know what will happen," Maria de los Angeles Pichardo, who left with her husband and son, told AFP news agency. "To be safe, we prefer to cross."