Venezuelan opposition candidate Henrique Capriles says his campaign will formally contest the official results of the presidential elections in a Supreme Court filing.
Capriles told a May Day rally the challenge would be presented to the top court on Thursday.
President Nicolas Maduro was declared the winner of the April 14 vote to replace the late Hugo Chavez as Venezuela's leader.
Opposition and government supporters flooded Venezuelan streets in rival May Day marches Wednesday as a continuing dispute over the election results kept political tensions high in the OPEC nation.
On Tuesday, several opposition lawmakers were injured in a brawl on the floor of Congress, a result of their refusal to recognize the Maduro presidency.
Some information for this report was provided by AP, AFP and Reuters.