The Venezuelan Democratic Action party reported that Luis Manuel Diaz, a regional opposition leader, was shot dead at a campaign rally.
Witnesses reported that attackers in a car open fired on Diaz while he was holding a public meeting in Guarico state.
Opposition leaders said that militias supporting the current governing United Socialist Party of Venezuela were to blame for the murder of Diaz.
Democratic Action party leaders are demanding that authorities carry out a thorough investigation and bring to justice those responsible for this horrific crime.
Opposition politicians say that their candidates have been attacked on several occasions in these last weeks leading up to parliamentary elections.
The Venezuelan government has denied any involvement with attacks against the opposition movement who currently holds a majority of seats in parliament.