(CNN) Opponents of Venezuelan President Nicolás Maduro are calling for continued protests ahead of Sunday's controversial election, a day after demonstrators clashed with national guard troops in the capital in defiance of a protest ban.

Opposition leaders have vowed unrest before the election of a "constituent national assembly" that would rewrite the constitution at Maduro's request -- a move that the leftist leader's critics say could consolidate his power and lead to a dictatorship.

Venezuelan police line up before clashing with opposition activists on Thursday, April 6.

Venezuelan police line up before clashing with opposition activists on Thursday, April 6.

Thousands of demonstrators protest against Maduro in Caracas on Saturday, April 8.

Thousands of demonstrators protest against Maduro in Caracas on Saturday, April 8.

Demonstrators help a journalist whose leg was injured while covering clashes in Caracas on April 10.

Demonstrators help a journalist whose leg was injured while covering clashes in Caracas on April 10.

Clouds of tear gas spread across a highway in Caracas during clashes on Monday, April 10.

Clouds of tear gas spread across a highway in Caracas during clashes on Monday, April 10.

A protester suffering from the effects of tear gas is carried away on Thursday, April 13.

A protester suffering from the effects of tear gas is carried away on Thursday, April 13.

Rescue workers tend to a demonstrator hit by a tear gas canister during anti-government protests on April 19.

Rescue workers tend to a demonstrator hit by a tear gas canister during anti-government protests on April 19.

Riot police clash with demonstrators while tear gas fills the air in Caracas on April 19.

Riot police clash with demonstrators while tear gas fills the air in Caracas on April 19.

A demonstrator stands in front of an armored vehicle during protests in Caracas on Wednesday, April 19.

A demonstrator stands in front of an armored vehicle during protests in Caracas on Wednesday, April 19.

A demonstrator catches fire during protests in Caracas on May 3. It happened as protesters clashed with police and the gas tank of a police motorcycle exploded. Other photos from the scene showed the man being attended for burns to his body.

A demonstrator catches fire during protests in Caracas on May 3. It happened as protesters clashed with police and the gas tank of a police motorcycle exploded. Other photos from the scene showed the man being attended for burns to his body.

An armored National Guard vehicle runs over a protester in Caracas on Wednesday, May 3. The protester, 22-year-old Pedro Michell Yaminne, survived, his mother told CNN. Interior and justice minister Nestor Reverol told reporters that the "lamentable" incident was under investigation. He said that moments before Yaminne was run over, demonstrators hurled a Molotov cocktail at the armored vehicle, opened the side door and "brutally assaulted" the driver.

Opposition activists clash with riot police in Caracas on Monday, May 8.

Opposition activists clash with riot police in Caracas on Monday, May 8.

Thousands of Venezuelan protesters march on a Caracas highway on Wednesday, May 10.

Thousands of Venezuelan protesters march on a Caracas highway on Wednesday, May 10.

Opposition activists scuffle with riot police in Caracas on May 12.

Opposition activists scuffle with riot police in Caracas on May 12.

During a "Grandparents' March" in Caracas, a man is blocked by police from reaching the Government Ombudsman's Office on Friday, May 12.

A street in eastern Caracas is painted with the names of people killed during more than two months of protests.

A street in eastern Caracas is painted with the names of people killed during more than two months of protests.

People flee during a clash between opposition demonstrators and riot police in Caracas on June 19.

People flee during a clash between opposition demonstrators and riot police in Caracas on June 19.

An opposition activist displays bullet shells during an anti-government demonstration on Monday, June 19.

An opposition activist displays bullet shells during an anti-government demonstration on Monday, June 19.

Maduro holds up a copy of the Venezuelan constitution during a news conference at the presidential palace in Caracas on June 22. Maduro has called for changes to the constitution amid the unrest.

Maduro holds up a copy of the Venezuelan constitution during a news conference at the presidential palace in Caracas on June 22. Maduro has called for changes to the constitution amid the unrest.

Protester David Jose Vallenilla is shot through a fence by a member of the National Guard near a military base in Caracas on Thursday, June 22. Vallenilla later died in the hospital after suffering three gunshot wounds to the chest.

Protester David Jose Vallenilla is shot through a fence by a member of the National Guard near a military base in Caracas on Thursday, June 22. Vallenilla later died in the hospital after suffering three gunshot wounds to the chest.

Protesters tear down a fence at the La Carlota airbase outside Caracas on Friday, June 23. A soldier shot a demonstrator through the fence at the base on the previous day, killing him.

National Guard members clash with deputies of the National Assembly in the Parliament's courtyard in Caracas on Tuesday, June 27.

National Guard members clash with deputies of the National Assembly in the Parliament's courtyard in Caracas on Tuesday, June 27.

Venezuelan lawmakers Luis Stefanelli, left, and Jose Regnault appear stunned in a corridor of the National Assembly after a clash with demonstrators in Caracas on Wednesday, July 5. Supporters of Maduro stormed the building and attacked opposition lawmakers, witnesses said. At least seven legislative employees and five lawmakers were injured, according to National Assembly President Julio Borges. Journalists said they were also assaulted.

Venezuelan police Officer Oscar Perez joins in an anti-government protest in Caracas on Thursday, July 13. Perez allegedly piloted a stolen police helicopter used to attack the Venezuelan Supreme Court with grenades on June 27.

A demonstrator dressed as Venezuelan independence hero Simon Bolivar is silhouetted against a national flag in Caracas on Monday, July 24.

A demonstrator dressed as Venezuelan independence hero Simon Bolivar is silhouetted against a national flag in Caracas on Monday, July 24.

A member of the National Guard fires at protesters during clashes in Caracas on Friday, July 28.

A member of the National Guard fires at protesters during clashes in Caracas on Friday, July 28.

A protester wounded by a pellet gun receives attention July 30 during a demonstration against the vote for a Constituent Assembly.

A protester wounded by a pellet gun receives attention July 30 during a demonstration against the vote for a Constituent Assembly.

A demonstrator shouts slogans through a traffic cone during an anti-government protest in Caracas on July 30.

A demonstrator shouts slogans through a traffic cone during an anti-government protest in Caracas on July 30.

A wounded anti-government demonstrator is helped by medics during clashes with police in Caracas on July 30.

A wounded anti-government demonstrator is helped by medics during clashes with police in Caracas on July 30.

Members of Venezuela's national police are caught in an explosion as they ride motorcycles near Altamira Square in Caracas on July 30. Venezuela has seen widespread unrest since March 29, when the Supreme Court dissolved Parliament and transferred all legislative powers to itself. The decision was later reversed, but protests have continued across the country, which is also in the midst of an economic crisis.

Maduro celebrates the results of a national vote on Sunday, July 30. His opponents boycotted the election and demonstrated against it for weeks, saying he orchestrated it to get around the existing National Assembly, which the opposition has controlled since 2015. Maduro has argued that the Constituent Assembly will help bring peace to a polarized country, with all branches of the government falling under the political movement founded by his late mentor and predecessor, Hugo Chavez.

Maduro celebrates the results of a national vote on Sunday, July 30. His opponents boycotted the election and demonstrated against it for weeks, saying he orchestrated it to get around the existing National Assembly, which the opposition has controlled since 2015. Maduro has argued that the Constituent Assembly will help bring peace to a polarized country, with all branches of the government falling under the political movement founded by his late mentor and predecessor, Hugo Chavez.

Opposition lawmaker Juan Requesens addresses a rally in Caracas on July 31. Two other leading opposition figures, Leopoldo Lopez and Antonio Ledezma, were rounded up from their homes, according to their families.

A woman in Caracas attends a vigil Monday, July 31, for anti-government activists who have died in the country's recent unrest. More than 120 people have been killed in Venezuela since early April, according to the attorney general's office.

Diosdado Cabello, a member of Venezuela's National Constituent Assembly, holds an image of Venezuela's late President Hugo Chavez as delegates gather for a group photo following their swearing-in ceremony on Friday, August 4.

Diosdado Cabello, a member of Venezuela's National Constituent Assembly, holds an image of Venezuela's late President Hugo Chavez as delegates gather for a group photo following their swearing-in ceremony on Friday, August 4.

Venezuela's Chief Prosecutor Luisa Ortega Diaz, third from left, is surrounded by employees of the General Prosecutor's office as she is barred by security forces from entering her office in Caracas on Saturday, August 5.

Members of the Venezuelan armed forces fly over Valencia in a helicopter while citizens demonstrate in support of a group that staged a paramilitary uprising at the Paramacay military base on August 6.

Members of the Venezuelan armed forces fly over Valencia in a helicopter while citizens demonstrate in support of a group that staged a paramilitary uprising at the Paramacay military base on August 6.

A man is arrested in Valencia during clashes between anti-government activists and the National Guard on August 6.

A man is arrested in Valencia during clashes between anti-government activists and the National Guard on August 6.

Soldiers stop a vehicle and detain its passengers on the Paramacay military base in Valencia, Venezuela, on August 6. According to authorities, two people were killed when an anti-government paramilitary attack was quelled at the base.

A costumed demonstrator in Caracas, Venezuela, protests the government of Venezuelan President Nicolas Maduro on Sunday, August 6. Unrest continued to sweep through the country after a new legislative assembly was inaugurated following a controversial election on July 30. The new assembly has wide-ranging powers and is expected to rewrite the Venezuelan constitution at Maduro's behest. Opposition supporters, who see the vote as a power grab and an erosion of democracy, boycotted and staged demonstrations against the vote.

Protesters threw Molotov cocktails and troops fired rubber bullets in the air Friday afternoon in one part of the capital, Caracas, video distributed by Reuters showed. Dozens of people were arrested, Reuters reported.

Maduro's regime has forbidden protests through Tuesday, saying violators will face prison terms of five to 10 years. It says it has dispatched more than 370,000 troops across the country to secure Sunday's vote.

The opposition wants to stop the election, which likely would favor Maduro as his opponents largely are not running.

Opposition leaders have called for protesters to gather Sunday at a freeway in Caracas and main streets throughout the country.

"What are they going to do? Arrest millions of people who protest?" opposition leader Henrique Capriles told reporters Friday.

Protesters blocked more than a dozen intersections Friday in Caracas. In one instance, about 120 people gathered at and near an intersection in the Altamira neighborhood.

Defiant Caracas residents cover their faces and stay on the streets Friday even though this is now illegal starting today. They are their own trancas - blockades - on the streets. @cnn #Venezuela A post shared by Khushbu Shah (@khushbuoshea) on Jul 28, 2017 at 10:34am PDT

People wearing masks blocked the intersection, in part with bricks, wire, tires and other debris on the street. Some held signs critical of Maduro.

At one protest site, paramedic Johann Paredes, 27, helped both injured protesters and national guard troops Friday. He says he tries to be apolitical.

"But if I take my helmet off, I would say I'm totally against" the vote, he said. "Honestly, I'm terrified that (it) is going" forward. "It's a disaster."

National guard troops in riot gear stand behind shields during a protest Friday in Caracas.

Maduro, who has said that rewriting the constitution is needed to restore order, told a rally earlier this week in Caracas that he has proposed talks with the opposition.

Opposition leaders have said they are willing to talk only if Sunday's vote is postponed. Maduro on Saturday claimed that there were discussions that brought the two sides close to agreement, but talks fell apart. He blamed opposition leader and National Assembly Vice President Freddy Guevara for the breakdown.

Sunday's election: What's at stake

Voters Sunday will elect a 545-seat assembly that could do whatever it wants in rewriting the constitution -- including abolishing the current National Assembly and even removing Maduro, said Luis Vicente Leon, a Venezuelan political analyst and college professor.

An anti-government activist is arrested Friday during clashes in the capital, Caracas.

But Maduro called for the constitutional revisions, and with pro-Maduro candidates running for many of the seats, including former ministers in his government, the body is likely to favor him. The assembly could give Maduro new powers and dissolve state institutions.

Though the opposition won control of the National Assembly in 2015 elections, it is essentially void because pro-Maduro legislators stopped attending sessions.

More than 350 members of the new assembly are to be elected in open municipal votes. The remaining members will be elected by people from certain social and industry groups (like students, pensioners or workers).

Voters are being told they can go to any polling station in their municipalities in case protesters block access.

Cilia Flores, Maduro's wife and a candidate for the new assembly, has said the new pro-Maduro members will install a separate justice commission "to determine those responsible for these terrible damages," including politicians who she says has promoted violence.

In a nonbinding July 16 referendum organized by opposition parties, an overwhelming majority of voters came out against Maduro's plan.

The referendum asked voters three yes-no questions. More than 98% of voters chose to reject the proposed constitutional assembly, request the military defend the existing constitution and support fresh elections before Maduro's term ends in 2019.

The turnout represented about 37% of Venezuela's total electorate.

Colombia: New assembly won't be recognized

International pressure against Venezuela's election has been increasing. In the past few days, the United States , Mexico and Colombia said they're freezing assets and imposing other restrictions on certain current and former Venezuelan government officials.

A protester faces off against national guard troops as clashes continued Friday in Caracas despite rain.

The United States would follow up with further "strong and swift economic action" if the vote happens, senior US officials have said.

Colombian President Juan Manuel Santos said Friday his government will not recognize Venezuela's constituent assembly.

The assembly has a "fake origin and therefore, the results will not be recognized," Santos said in Barranquilla.

Colombia is pushing for a "peaceful solution, hopefully a fast and democratic one, so that the nation that we love -- and I want to once again express my solidarity with the people of Venezuela -- will soon come out from the darkness," Santos said.

The relationship between the neighbors has been strained for years.

Maduro on Saturday called Santos a slave of the United States.

Deadly protests

For months, violence has spiraled out of control as the struggle for food and medicine grows.

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Political upheaval intensified in late March when the Venezuelan Supreme Court dissolved Parliament and transferred all legislative powers to itself. The court reversed that decision after three days, but the initial move triggered intermittent, deadly protests for months.

As of Friday, at least 113 people have died in protests and other incidents linked to the unrest, the attorney general's office has said, often without elaborating on who was responsible for their deaths.

At least seven of those deaths happened Wednesday and Thursday during a two-day opposition-led general strike

Maduro and Chavez

Maduro is aligned with the political movement of Hugo Chavez, the President from 1999 until his death in 2013. Under constitutional changes Chavez ushered in, presidents can run for an unlimited number of six-year terms.

Chavez trumpeted a brand of socialism -- dubbed Chavismo -- in which he increased subsidies to the poor and fixed prices for goods, but alienated Venezuela from foreign investors who were spooked by his anti-American rhetoric. Maduro, elected as Chavez's successor in 2013, kept up his predecessor's practices.

Venezuela became dependent on selling its oil abroad, and income suffered when the price of oil per barrel dropped from $100 in 2014 to $26 in 2016. Inflation has soared, and unemployment could reach 25% this year, according to the International Monetary Fund.

Maduro has long verbally clashed with opposition leaders. The opposition wanted to impeach Maduro after it won a National Assembly majority, but he stacked the Supreme Court with his supporters, blocking any impeachment attempts.