Police officers fired tear gas, pellet guns and water cannon to disperse a crowd marching toward the National Assembly, the seat of the powerful new legislative body, according to El Nacional.
Venezuelan opposition lawmaker Amelia Belisario was reportedly taken to hospital with a wrist injury after she was hit by a tear gas canister fired by the National Guard.
Passers-by, including children and old people, were also caught up in clashes and suffered from tear gas inhalation, the news outlet reported.
More than 40 percent of Venezuelans voted last Sunday to convene the constituent assembly, although opposition leaders say the government inflated the turnout figures. The body, which was sworn in earlier in the day, will rewrite the constitution in a bid to bring peace to the country.