Later yesterday in the opposition hotbed of San Cristobal near the Colombia border, university student Paola Ramirez died after being shot by men pursuing her and her boyfriend, according to relatives and witnesses.
Opponents are pushing for Maduro's removal through early elections and the release of dozens of political prisoners.
President Maduro has accused the opposition of attacking the police and looting shops, and more than 30 arrests have been made.
Speaking to thousands of militia members dressed in beige uniforms gathered in front of the presidential palace to mark the force's seventh anniversary, Maduro said it is time for Venezuelans to decide if they are "with the homeland" or against it.
Venezuelan Ambassador Samuel Moncada spoke as the opposition and government supporters held dueling marches in Caracas.
Already drawing criticism for the GM seizure, Maduro announced late Thursday that he wanted an investigation into cellphone operator Movistar for allegedly being part of the "coup-minded march" organized by his adversaries Wednesday.
A Venezuelan teenager who was shot in the head near anti-government protests in the capital has died. That move raised an global outcry, and although the court mostly reversed itself the following day, Maduro's opponents found the spark they needed to launch a new protest movement.
Marchers in the opposition demonstration in Caracas included Liliana Machuca, who earns about $20 a month holding two jobs teaching literature.
'They've got the right to march but marching isn't burning stuff, throwing rocks, ' said Jahil Marcano, a 48-year-old construction worker who had joined the pro-government rally. Although she doesn't expect change overnight, she said protesting is the only option the opposition has after what she says are scores of abuses committed by the government.
"This is like a chess game and each side is moving whatever pieces they can", said Machuca, her face covered in a white, sticky substance to protect herself from the noxious effects of tear gas.
"I came to march to defend the country and defend the president who we voted for", she said.
The State Department and several regional governments have deplored excessive violence by security forces and pro-government groups.
"We are extremely concerned that Rosneft's control of a major U.S. energy supplier could pose a grave threat to American energy security", six senators wrote in an April 4 letter to the U.S. Treasury secretary.
Late Tuesday, on national television, Maduro reasserted his earlier claims that the United States is behind opposition marches, saying the U.S. State Department had given the green light for a coup attempt. He has also warned that an opposition government would slash social benefits like healthcare for the poor and subsidized food.
Maduro this week said he was dramatically expanding civilian militias created by Chavez and giving each member a gun.
The remarks come a day after the U.S. State Department issued a statement warning the South American country, "Those responsible for the criminal repression of peaceful democratic activity. and for gross violations of human rights, will be held individually accountable for their actions by. the global community".
In Western Caracas, red-clad government supporters - some wearing ski masks - were patrolling the streets close to an opposition rallying point.