President Hugo Chavez vowed on Sunday to run a more efficient government if he wins Venezuela's election next weekend while rival Henrique Capriles demanded justice for the shooting of two opposition activists.

With the South American OPEC member's October 7 presidential vote shaping into a close fight, Capriles is hammering Chavez daily on his record with day-to-day problems such as crime, blackouts and shoddy infrastructure.

"Efficiency, that is one of my promises for the next period. We have to correct things," the 58-year-old president said in his most direct comment on a theme the opposition hopes could sway former "Chavistas" into their camp.

In recent days, Chavez has added into his campaign speeches an acknowledgement of Venezuelans' frustration with grassroots problems but has said things would be far worse under Capriles, who he paints as a heartless capitalist elitist.

Capriles, 40, a state governor who has a centrist vision of business-friendly government with strong welfare policies, lambasted the government overnight for the fatal shootings of two local opposition leaders in Barinas state.

"We demand an immediate investigation into something that should have never have occurred - a campaign motorcade attacked with gunshots," Capriles said on Twitter.

"We Venezuelans are sick of violence and we are going to defeat it, along with its government, on the 7th of October ... The violent discourse of the government candidate will be defeated."

Gunmen killed the two activists, including one from Capriles' First Justice party, at a rally on Saturday afternoon in the worst violence of the volatile election campaign.

The party said gunmen had fired from a van, which witnesses identified as belonging to a state institution, after Chavez supporters blocked an opposition motorcade.

The government did not confirm that version but promised an investigation into what it said was an isolated incident.

Venezuela is awash with arms, and voters cite violent crime as their No. 1 worry. There had been some gunshots and clashes at previous opposition rallies but no deaths.

TIGHT RACE

With one week to go, polls are mixed, leading both sides to claim they are heading for victory. Venezuelans are fearful of violence if the result is close and then disputed by one side.

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

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

He was campaigning in two states on Sunday while Capriles was hoping for his biggest turnout yet at a rally in Caracas.

Western investors hope the more business-friendly Capriles will win and end a nationalization drive and other radical policies that have polarized Venezuela like never before and made Chavez one of the world's most controversial leaders.

Chavez promises to "deepen" socialism if he wins. That would likely mean continued spending on his popular welfare "missions," more investment from politically aligned allies like China and Iran, new confrontations with Venezuela's private sector and continued support for fellow leftists governments in Latin America such as Cuba and Nicaragua.

"The first thing we are going to do with our victory is something like put a lockdown on what we have achieved, to prevent any going backwards. That would be terrible," Chavez said in an interview on state TV.

After election wins in the past, Chavez has launched nationalization or constitutional reform drives.

Opposition leaders are angry at Chavez's use of state resources in his campaign but say the electronic-based vote system should be hard to rig on election day, since they will have their own observers at most voting booths.