Opposition protesters have clashed with riot police in chaotic scenes in cities across Venezuela.
A rally in Caracas began peacefully before masked youths hurled rocks and fire bombs as they took part in a march of thousands towards parliament.
A teenager protester died, as police used rubber bullets and water cannons.
The government has warned demonstrators - who have been protesting for a month - that their right to cause street disruption is not absolute.
Justice and Interior Minister Nestor Reverol warned that blocking the highways carried an eight-year sentence.
The demonstrators are especially angry over President Nicolas Maduro's recent decree that creates a 500-member constituent body to rewrite the constitution, a step that would bypass the opposition-controlled National Assembly.
Speaking at the National Electoral Council, Mr Maduro said there would be elections for the new citizens' assembly in a few weeks.
More than 30 people have been killed and hundreds either injured or arrested since protesters took to the streets in early April.
Demonstrators on Wednesday - many wearing bandanas and carrying catapults - confronted the security forces on the Francisco Fajardo highway, which runs through the heart of Caracas.
"They [the security forces] are mobilised as if this was a war," opposition leader Henrique Capriles said.
Mr Maduro succeeded Hugo Chavez, a popular leader, who had introduced wide-ranging social welfare programmes and died in 2013.
Since then, falling prices for Venezuelan oil exports have cut government revenue and there have been shortages of food, baby milk, medicine and other basics.
The International Monetary Fund has forecast that inflation in Venezuela will be above 700% this year.
Presidential elections are due at the end of next year.