Hours before voting began, an oil pipeline in the west of the country was damaged in a blast that the government said was terrorism.
Jose Vicente Rangel, the vice-president, said on state television: "This is a miserable terrorist attack."
Rafael Ramirez, the energy minister, said the blast at a pipeline supplying the country's huge Amuay-Cardon refinery had not affected fuel supplies and that the fire was under control.
Chavez, a former army officer allied with Cuba, has accused Washington for orchestrating the opposition walkout to try to
destabilise his. But he said the boycott included only a minority of candidates who will not invalidate the vote.
Main opposition groups said they would abstain from voting after accusing electoral authorities of favouring the populist, left-wing leader and manipulating electronic voting machines. They had previously agreed to participate in the election.
Polls indicated a convincing lead for deputies backing President Chavez even before the boycott was announced.
Pedro Zamora, a pensioner who was voting in eastern Chacao district, said: "The opposition are just a bunch of thieves who tried to sabotage the election. We can see the government are going to get most of the votes."