The European Union Thursday expressed concern about rising violence linked to Venezuela’s elections after the murder of a leader of the opposition, which appears poised to win control of parliament for the first time in 16 years.

The European Union Thursday expressed concern about rising violence linked to Venezuela's elections after the murder of a leader of the opposition, which appears poised to win control of parliament for the first time in 16 years.

"Yesterday's assassination of Mr Luis Manuel Diaz, the regional secretary of the Accion Democratica party, marks a further deterioration of an already tense situation in the run up to the parliamentary elections on 6 December 2015," the EU said in a statement.

"This killing adds up to a worrying tendency of (an) increasing number of violent attacks linked with the electoral campaign."

It called for a swift investigation and said those responsible must be brought to justice.

"The EU calls on Venezuelan authorities to guarantee that the electoral campaign can take place in a peaceful and orderly environment," the statement said.

Diaz was shot dead Wednesday evening in the central Guarico region at a campaign rally for the legislative elections.

Opinion polls indicate that the opposition is poised to win control of the National Assembly for the first time since Maduro's mentor, late leftist Hugo Chavez, came to power in 1999.