(Adds U.S. embassy, arrest figures, opposition comment)
CARACAS, July 27 (Reuters) - Clashes between Venezuelan security forces and demonstrators have killed five people during the latest opposition-led strike to protest an election on Sunday that critics contend will mark the end of democracy in the oil-rich country.
As Venezuela's crisis deepened, Colombian airline Avianca on Thursday canceled its operations in the country and the U.S. State Department said it was ordering family members of U.S. employees at its embassy in Caracas to leave ahead of the vote.
The controversial Constituent Assembly election is scheduled for July 30.
Critics of President Nicolas Maduro were planning to pile more pressure on the unpopular leftist leader by holding a major protest dubbed 'The takeover of Venezuela' on Friday.
"If yesterday and today the streets were empty, tomorrow we must take over all of Venezuela," said opposition lawmaker Freddy Guevara, referring to a two-day anti-government strike that started on Wednesday.
Interior Minister Nestor Reverol warned that protests were banned from Friday to Tuesday, leaving open the likelihood of more violence in volatile Venezuela. Many Venezuelans are nervous and have been stocking up on food and staying home.
On Thursday, the U.S. State Department also authorized the voluntary departure of U.S. government employees at its embassy in Caracas.
President Donald Trump has warned that his administration could impose economic sanctions on Venezuela if Maduro goes ahead with the vote to create a legislative superbody known as the Constituent Assembly.
The Constituent Assembly would have power to rewrite the constitution and shut down the existing opposition-led legislature, which the opposition maintains would cement dictatorship in Venezuela.
At least 108 people have died in anti-government unrest convulsing Venezuela since April, when the opposition launched protests demanding free and fair elections to end nearly two decades of socialist rule.
(For graphics on Venezuela's economic crisis and anti-government protests see: http://tmsnrt.rs/2pPJdRb and http://tmsnrt.rs/2ujuylf)
Many streets remained barricaded and deserted on Thursday as a nationwide work stoppage entered its second day.
Plenty of rural areas and working-class urban neighborhoods were bustling, however, and the strike appeared less massively supported than a one-day shutdown last week.
With Venezuela already brimming with shuttered stores and factories, amid a blistering four-year recession, the effectiveness of any strike can be hard to gauge. Many Venezuelans live hand-to-mouth and say they must keep working.
In Barinas, home state of former Venezuelan leader Hugo Chavez, only about a third of businesses were closed according to a Reuters witness, as opposed to the opposition's formal estimate of 92 percent participation nationally.
"I am opposed to the government and I agree we must do everything we can to get out of this mess, but I depend on my work. If I don't work, my family does not eat," said Ramon Alvarez, a 45-year-old barber at his shop in Barinas.
Adversaries have said that the ruling Socialist Party wants to consolidate dictatorship with Sunday's vote. There has been widespread international condemnation of the ballot, and the United States on Wednesday announced sanctions against 13 current and former officials for corruption, undermining democracy, and participating in repression.
Government officials and candidates for the Constituent Assembly wrapped up campaigning on Thursday with a rally in Caracas with Maduro.
The leftist leader reiterated that the assembly was the only way to bring peace to Venezuela, blasted threats of further sanctions from "emperor Donald Trump," and hit back at accusations that he is morphing into a tyrant.
"The usual suspects came out to say Maduro had become crazy," he told cheering red-shirted supporters in Caracas. "Of course, I was crazy! Crazy with passion, crazy with a desire for peace."
Amid rumors of 11th-hour attempts to foster negotiations, Maduro reiterated an invitation to dialogue with the opposition, although such talks have flopped in the past.
The state prosecutor's office said a 49-year-old man was killed during a protest in Carabobo state and a 16-year old died in the middle class area of El Paraiso in Caracas on Thursday.
A 23-year-old man and a 30-year-old man were killed in western Merida state and a 16-year-old boy was killed in the poor Caracas neighborhood of Petare during clashes on Wednesday.
Five people were also killed in unrest during last week's one-day strike.
Over 190 people were arrested during the stoppage on Wednesday, said local rights group Penal Forum. Since April, authorities have rounded up nearly 4,800 people, of whom 1,325 remain behind bars, the group said.
Voters on Sunday will choose 364 constitutional representatives distributed across municipalities and state capitals and another 181 "sectoral" candidates from demographic groups ranging from students to farmers and fisherman.
The opposition Democratic Unity coalition is boycotting the vote. They have said that the use of sectoral candidates, who had to collect signatures and file them to the government-leaning elections council, was a way to weed out anti-government aspirants.
(Additional reporting by Deisy Buitrago, Brian Ellsworth, Alexandra Ulmer, Anggy Polanco, Andrew Cawthorne, Diego Ore, and Girish Gupta in Caracas, Mircely Guanipa in Punto Fijo, Francisco Aguilar in Barinas and Maria Ramirez in Bolivar; Writing by Andrew Cawthorne and Alexandra Ulmer; Editing by Tom Brown, Toni Reinhold)