At least one person has died in renewed violence in Venezuela, as thousands of opponents of President Nicolas Maduro staged sit-ins and roadblocks across the country in a seventh week of anti-government rallies.

Luis Alviarez, 18, was killed during protests in the western state of Tachira after being shot by gunfire in the thorax, prosecutors said, without giving further details. That brought the death toll since the start of the protests to at least 39 people.

Demonstrators have been on the streets daily since early April to press for elections, blaming Maduro for an economic crisis that has caused severe shortages of food and medicine.

The president accuses protesters of seeking a violent coup, and says he is the victim of an international right-wing conspiracy that has already brought down leftist governments in Brazil, Argentina and Peru in recent years.

The government and the opposition have blamed each other of sending armed groups to sow violence in the protests. Police have blocked marches with tear gas, pepper spray and water cannons, while protesters have hurled rocks and Molotov cocktails, vandalised property and started fires in a near-daily series of clashes.

Sit-ins and roadblocks

On Monday, protesters stayed on Caracas' main roads for six hours, then began to disperse under a heavy rain in late afternoon. Others vowed to stay rain or shine for the full 12 hours of the sit-in.

"I'm here for the full 12 hours. And I'll be back every day there's a protest, for as long as is necessary," Anelin Rojas, a 30-year-old human resources worker, told the Reuters news agency.

"Unfortunately, we are up against a dictatorship. Nothing is going to change unless we force them," Rojas added, surrounded by placards saying "Resistance!" and "Maduro, Your Time Is Up!"

OPINION: Why is Venezuela in crisis again?

In Tachira, some farmers were striking in solidarity with the protesters, while on Margarita island, opposition politician Yanet Fermin was detained while mediating between security forces and protesters, her party said.

In Valencia, three policemen were injured, authorities said, with one mistakenly reported by the local Socialist Party governor as having been shot dead earlier in the day.

The opposition, which commands majority support after years in the shadow of the ruling socialists, is more united than during the last wave of anti-Maduro protests in 2014.

Escalating crisis

The protests that erupted after the government-stacked Supreme Court issued a ruling March 29 nullifying the opposition-controlled National Assembly, a decision it later reversed amid a storm of domestic and international criticism.

The government is also setting up a controversial body called a constituent assembly, with authority to rewrite the constitution and shake up public powers.

Maduro says that is needed to bring peace to Venezuela, but opponents view it as a cynical tactic to buy time and create a biased body that could perpetuate the socialists' rule.

"There's a real situation of crisis in the country, and the opposition says they will not give up until elections are called," Al Jazeera's John Holman, reporting from Cucuta, in Venezuela's border with Colombia, said.