The 14-year-old boy and another protester were shot dead in the western city of Barquisimeto on Tuesday night.
The local governor blamed armed government supporters. Two students were killed during protests last week.
Nicolas Maduro's presidency has come under increasing pressure as the economy suffers and opponents accuse him of creating a dictatorship.
Mr Maduro was pelted with objects by angry protesters as he left a military event in the south-eastern state of Bolivar earlier on Tuesday.
The latest anti-government demonstrations were sparked by a decision on Friday to bar opposition leader Henrique Capriles from holding public office for 15 years.
The dead teenager was identified as Brayan Principal by opposition MP Alfonso Marquina, who said he had been shot in the abdomen.
A 36-year-old man was also killed in Barquisimeto in a separate incident, the state prosecution service said.
Opposition leaders are calling for a date to be set for postponed regional elections.
Mr Maduro has resisted efforts by the opposition to hold a referendum on removing him and has vowed to continue the "socialist revolution" launched by his predecessor Hugo Chavez.
He says the economic crisis and efforts to get rid of him are a capitalist conspiracy.
A teenage demonstrator has been killed during growing unrest in Venezuela, as political and economic crisis deepens.