Opposition leader Henrique Capriles demands investigation into shooting that killed two politicians and one supporter.

A third opposition supporter has died from a shooting at a rally this weekend, that was the worst violence of Venezuela’s volatile election campaign, presidential candidate Henrique Capriles said.

“We are going to defeat violence in Venezuela,” Capriles told a rally in Caracas on Sunday, after confirming the third fatality in the confrontation at an opposition event in Barinas state on Saturday.

Capriles demanded an investigation into the fatal shooting that killed two opposition politicians from Capriles’ party, Primero Justicia (First Justice), and one supporter.

The gunman reportedly started shooting during an argument which broke out after a group of Chavez’s supporters blocked a campaign caravan.

The government of President Hugo Chavez, who is seeking re-election, confirmed the deaths and vowed the perpetrators would be brought to justice.

Tareck El Aissami, the interior minister, said the shooting happened when loyalists of both candidates faced off on a road between the communities of Barinas and Barinitas, about 450km southwest of Caracas, but he did not say anything about the dead men’s political affiliation.

Opposition politician Julio Cesar Reyes said a group of Chavez supporters blocked a motorcade of Capriles backers and people on both sides were arguing when a man appeared with a gun and started shooting.

The interior minister said police were still investigating.

Venezuela is awash with guns, and violent crime is frequently cited as voters’ main concern. There had been shootings and fistfights in previous opposition rallies as “Chavistas” and Capriles’ supporters clashed, but no deaths.

“This tragedy gives us more strength and faith to fight for a Venezuela where justice and non-violence reign,” Primero Justicia said in a statement on Saturday.

One of the victims was from its party and another from Accion Democratica (Democratic Action), it said.

Primero Justicia said that witnesses identified the offending vehicle as belonging to state oil company PDVSA or the local mayor’s office. It also said another two people were injured and there were six arrests after the attack on the motorcade, but this account was not confirmed by police or other authorities.

Tight presidential race

Meanwhile, on the campaign trail, Chavez showed off new infrastructure projects in Caracas, while Capriles accused him of wasting Venezuela’s money on foreign allies.

With polls inconclusive, both men are wooing undecided voters in what looks likely to be the tightest presidential election of the charismatic socialist leader’s 14-year rule.

Despite two bouts of cancer since mid-2011, Chavez, 58, has declared himself completely cured and is trying to recapture some of his old panache and energy to win a new six-year term.

On Saturday, he inaugurated a monorail, then inspected extensions to the subway system, and a cable car in poor areas of Caracas typical of his power base. The projects cost a combined $2.5bn.

“We are not thinking about making money. That’s the difference with capitalism,” Chavez said in Petare, one of the largest slums in Latin America.

“The loser will have to go to the moon and see if he can govern a rock there because here the bourgeoisie are never coming back,” Chavez quipped of Capriles, whom he portrays as representing a heartless, right-wing elite.

Capriles, a 40-year-old state governor who has a centrist political vision and sees Brazil’s mix of free-market economics and strong welfare polices as his model, has been crisscrossing Venezuela all year in an exhausting campaign.

Addressing thousands in Falcon state, in west Venezuela, Capriles accused Chavez of making false promises to the public, while squandering oil revenues on foreign allies.

“The government prefers to build a refinery in Nicaragua, or send oil and worry about power cuts in Cuba, but it doesn’t care about blackouts here in Falcon,” he said.

Of the six or so best-known pollsters in Venezuela, a majority put Chavez ahead, but they also show Capriles creeping up in recent weeks, and two put him just ahead.

Venezuelans are transfixed by the race, but also nervous of possible violence if the result is close and disputed.