By Andreina Aponte and Eyanir Chinea
CARACAS (Reuters) - Venezuela opposition lawmakers placed pretend coffins and body bags at gates of the National Guard headquarters on Tuesday in protest after the latest fatality in anti-government unrest that has killed at least 75 people since April.
Footage and photos from demonstrations on Monday showed at least three members of the National Guard - a military unit with public order responsibilities - aiming and firing pistols in clashes on a major Caracas highway.
Seventeen year-old demonstrator Fabian Urbina was shot in the chest and died, and several others were injured.
"You cannot keep killing people in the street!" opposition lawmaker Tomas Guanipa shouted, as the group harangued National Guard members during the early-morning protest in the middle-class El Paraiso zone of Caracas.
"Who gave the order to shoot?" asked another lawmaker Jose Olivares as soldiers watched silently from inside their base.
Venezuelan authorities said two National Guard members had been detained on Monday for what the interior minister called "presumed improper and disproportionate use of force" when thousands of protesters flooded the streets.
As well as the fatalities, there have also been thousands of injuries and arrests since Venezuela's opposition began its latest street campaign against President Nicolas Maduro's socialist government in early April.
They accuse Hugo Chavez's successor of becoming a dictator and wrecking the once-prosperous OPEC member's economy, and are demanding a presidential election to end his rule.
Maduro says "terrorists" and "fascists" are leading the protests in an effort to topple him by force as briefly happened to Chavez in 2002. Government supporters, bystanders and some members of the security forces have also been victims of the violence, with gunshot wounds the most common cause.
Many grassroots opposition supporters feel intimidated by the daily violence in cities around Venezuela, where masked youths barricade streets and hurl stones and Molotov cocktails against security forces with tear gas and water cannons.
There is also some exhaustion setting in after 80 days of what the opposition denominates "resistance".
But opposition leaders have vowed to step up tactics shortly to ramp up the pressure on Maduro, and called a news conference for Tuesday afternoon.
They are seeking to halt Maduro's plan for July 30 elections for a special assembly to rewrite the constitution, a move the opposition says is rigged to keep him in power.
(Additional reporting by Victoria Ramirez; Writing by Andrew Cawthorne; editing by Grant McCool)