A parliamentary candidate, an opposition activist and a 13-year-old boy were among at least 10 people killed on Sunday as President Nicolas Maduro defied international pressure and internal strife to hold a controversial election.

Anti-Maduro activists wearing hoods or masks erected barricades on roads, and scuffles broke out with security forces who moved in quickly to disperse demonstrators who denounced the election as a naked power grab by the president.

"This is war!" Caracas resident Conchita Ramirez exclaimed on television as she described troops firing at people and buildings in the capital.