A Venezuelan presidential candidate said  Saturday that three opposition activists were detained arbitrarily ahead of July elections in a campaign marred by allegations of political persecution.

"They have been missing since yesterday... It is an unjust and arbitrary detention," said Edmundo Gonzalez Urrutia of the Democratic Unitary Platform (PUD), the largest opposition coalition in Venezuela.

"It is not known at this moment where and how they are," Gonzalez Urrutia said of the three at a campaign event in Caracas.

The three missing people are Juan Iriarte, coordinator of opposition party Vente, and two activists of the Popular Will party, Luis Lopez and Jean Carlos Rivas.