Week-long protests in Venezuela turned violent on Wednesday leaving three people dead, more than 20 injured, and the president, Nicolás Maduro, struggling to restrain mounting discontent among opposition groups and radical elements of his Chavista movement.

Initially sparked by unrest over soaring inflation, rising crime and the arrests of student protesters, the demonstrations in Merida, Tachira and Anzoategui have escalated into deadly clashes between opposition activists and pro-government Chavista militias known as colectivos.

The president of the National Assembly, Diosdado Cabello, said the first killing was of a colectivo member in downtown Caracas during an opposition march.

Cabello blamed the opposition for the murder and assured the colectivos that those responsible would feel the full weight of the law. But tellingly, he also appealed to the armed groups not to take matters into their own hands. "Remain calm and sane," he urged in a televised address. "We ask you to trust us."

In the short term, the protests pose little threat to Maduro's government, but analysts see increasing confusion as armed militias enter the fray. Any loss of control over armed supporters could pose a bigger threat than the fragmented opposition.

"The risk of protests escalating will increase if upcoming demonstrations result in new violent actions against dissidents and particularly if the government is unable to control the intimidation tactics employed by the collective groups," said Diego Campos-Moya, an analyst at IHS Country Risk.

The colectivos, whose main turf is the 23 de Enero neighbourhood in western Caracas, were formed during the Chávez years to enforce the leftist ruler's government programmes. They double as neighbourhood organisations that run community improvement projects but can also act as vigilante groups that intimidate political opponents.

Self-proclaimed defenders of the revolution, the colectivos radio each other from the top of neighbourhood buildings whenever an unknown face comes into their area. In 23 Enero, even the police and National Guard consider the territory off-limits.

In the past, colectivos showed staunch support for Chávez, appearing en masse at political rallies and even disrupting opposition gatherings.

During this week's protests, thousands of Venezuelans took to Twitter to report disturbances across the country, many of which included clashes between colectivos and protesters.

"I saw how the police stood aside to let the colectivos control the city. It is a method frequently used by this government to intimidate opponents. They operate almost in parallel to the police, neutralising protesters, either by intimidation or by actual force," tweeted @Eurolobo, a journalist and blogger from Merida.

Other images and videos showed armed men on bikes tearing down gates and shooting at parked cars. The reports circulated through social networks and foreign broadcasters such as CNN Español, but were not shown on Venezuelan TV stations, because of what many here deem a self-imposed media blackout for fear of government retaliation.

The government denies accusations of censorship but has warned local and international media that it will punish organisations that release content likely to incite violence or be construed as "an apology for crime". On Wednesday night the Colombian news channel NTN Noticias was taken off-air during a broadcast of that day's street protests in Venezuela.

The protests, which started last Saturday in the state of Merida, were initially led by a group of students demanding the release of classmates who had been jailed after earlier protests and an attack on the governor's residence in the neighbouring state of Tachira.

Since then, the street actions have mushroomed to include people from all walks of life who have seen their salaries evaporate under the heat of inflation. Others have joined in to express their anger at a spiralling murder rate, or over food shortages.

But supporters of the government, which recently won a majority of governorships in regional elections, see the demonstrations as a desperate push to oust Maduro by the most radical wing of the opposition.

Javier Corrales, a political science professor at Amherst College, said the protests were some way from toppling the government, but they highlighted how far the country was from social stability.

"The government received an unexpected shock. Following the December 2013 regional election, in which Maduro's forces recovered some ground from the close presidential election in April 2013, the government came to think, erroneously, that the opposition was no longer a concern. The government has been reminded that it remains quite unpopular across a large sector of the country, and that they have no policy to deal with this discontent other than more threats."

On Thursday the government issued a warrant for the arrest of Leopoldo López, the leader of Popular Will, a small offshoot opposition party that beat Chavista candidates in several contested mayoralties in December's poll.

"I personally blame Leopoldo López for these vandalistic acts of violence. We have proof that he received both funds and training to carry these actions out," said Jorge Rodríguez, mayor of the municipality of Libertador, where protesters were filmed destroying the windows of several public buildings, upturning benches and burning tyres.

The colectivos have issued a statement saying they will respect social order but demanding that López be judged for Wednesday's acts of violence.

López, who has repeatedly asked his supporters to take to the streets in large numbers and to protest in "an irreverent manner", has blamed Maduro, suggesting it was the government that infiltrated the peaceful marches and caused the deaths.

"Maduro, you are well aware that what happened today was part of your plan. The wounded and the dead are your responsibility," López tweeted. "The truth is in photos and videos that people took. The colectivos and the police were the ones who shot."

López has not been seen or heard from since his arrest was ordered on Wednesday night. In the past he has promised he will not relent in his efforts or street actions until "a way of out of Maduro's government" is found.

Maduro has banned all forms of protest that have not been approved by the government. Close to 30 protesters have been detained for their part in Wednesday events, but such actions are unlikely to choke unrest.

Venezuelans are now bracing themselves for what seems likely to be a week of further tumult and polarisation. Some think this could work in Maduro's favour. The ruling camp has looked rudderless and ineffectual in tackling the country's dire economic woes, but the opposition demonstrations have unified support around the president.

"The protests turned Chavistas all the more entrenched in their convictions to defend this government at all costs, and this is good news for Maduro," Corrales said.

The prospects for healing social divisions look remote, and tackling an economy in dire straits appears even more difficult, but if Maduro can rein in the hotheads among his supporters he may yet come out of this latest period of instability stronger.