Several police officers have been injured in Venezuela’s capital Caracas after an explosion during anti-government demonstrations, as voting begins to elect an all-powerful constituent assembly.

Police fired tear gas trying to disperse hooded demonstrators who blocked roads in support of opposition parties who say President Nicolas Maduro has rigged the election to ensure his socialist party continues to dominate.

Despite polls showing some 70 percent of Venezuelans oppose the vote, President Maduro, widely disliked for overseeing an economic collapse during four years in office, has pressed ahead, vowing he would begin a “new era of combat” in the crisis-stricken nation.

That’s despite the threat of further U.S. sanctions and months of opposition protests in which more than 115 people have been killed, including three deaths over the weekend, where a candidate to the assembly was killed during a robbery.

The opposition is boycotting Sunday’s vote, accusing Maduro’s administration of threatening to fire state workers who don’t vote and taking away social benefits like subsidised food from recipients who stay away from the polls, as it wants to avoid low turnout that would further undermine his legitimacy.