Two local opposition leaders were killed Saturday in the western Venezuelan state of Barinas, according to the opposition First Justice party.
A caravan was stopped at a blockade, the party said in a statement. When the two leaders got out to ask permission to pass, gunmen opened fire, First Justice said.
Two other people were wounded and at least six were arrested, according to the party.
"This tragedy gives us more strength and more faith to fight for a Venezuela where justice reigns, not violence," it said.
Opposition candidate Henrique Capriles will face Venezuelan President Hugo Chavez in elections on October 7. Clashes have flared in the campaign before, but Saturday is thought to mark the first deaths.
State-run VTV, citing the country's interior and justice minister, identified the victims as 63-year-old Omar Ramon Fernandez Moreno and 32-year-old Antonio Valero Avila.
The men were shot and died from their injuries, VTV reported.
Venezuelan Justice and Interior Minister Tareck El Aissami vowed to hold those responsible for the violence accountable.