Posted with permission from dpa German Press Agency

Caracas (dpa) - Venezuela's opposition said anti-government protests that drew millions to the streets Wednesday would continue despite violent clashes that killed two young demonstrators.

"When millions took to the streets today, even more must go out tomorrow," opposition leader Henrique Capriles said announcing more protests for Thursday.

While official crowd estimates were not released, the opposition-allied Meganalisis polling institute estimated as many as 6 million Venezuelans joined demonstrations across the country against the government of President Nicolas Maduro - an estimated 2.5 million in the capital Caracas alone.

A young man and a woman were shot dead in protests that saw police fire tear gas to disperse massive crowds. More than 400 people were arrested, authorities said.

University student Carlos Moreno, 17, was shot in the head during demonstrations in Caracas and died following emergency surgery, family members told local news media.

The attorney general's office said it was investigating the incident, which opposition leaders blamed on armed gangs allegedly loyal to Maduro.

A second person identified by media as a 23-year-old university student was shot dead during protests in the western city of San Cristobal.

With Wednesday's deaths eight people have been killed in two weeks of protests against Maduro's government which have sparked violent clashes between police, demonstrators and armed gangs.

A cordon of police in riot gear fired tear gas on large crowds of anti-government demonstrators trying to march from opposition-controlled eastern districts of Caracas to the public ombudsman's headquarters in the city centre.

Police fired more tear gas on a group of demonstrators coming from the west, in an apparent attempt to prevent the marches from joining.

United States Secretary of State Rex Tillerson condemned the crackdown.

"We are concerned the government of Maduro is violating its own constitution and is not allowing the opposition to have their voices heard or allowing them to organize in a way that represents the voice of the Venezuelan people," he said in Washington.

Demonstrators are demanding elections and an end to Maduro's increasingly authoritarian regime with a day of mass protests to mark the fourth anniversary of his presidency. Maduro was elected in 2013 to a six-year term to succeed late president Hugo Chavez, the architect of Venezuelan socialism.

Thousands of people also turned out for pro-government marches in central Caracas, wearing red shirts to distinguish themselves from anti-government demonstrators in white.

Both sides claimed the Venezuelan flag's red, blue and yellow for their own on hats and banners.

Maduro on Wednesday accused the opposition of fomenting violence and called for elections to "put conspirators and the interventionist right in their place."

Earlier in the week he announced a plan to arm 500,000 civilian members of the National Guard, a move that was swiftly condemned by rights groups and the Organization for American States.

The protests were set off by a failed power grab by the loyalist Supreme Court, which in a March 30 ruling attempted to strip the opposition-controlled National Assembly of its powers.

Venezuela's political crisis has escalated in recent months alongside an economic crisis that has caused widespread shortages of food and medicines.