(CNN) The United Nations Human Rights Office says at least 40 Venezuelans have died in recent protests over the power struggle between President Nicolas Maduro and self-appointed interim president Juan Guaidó.
CNN cannot independently verify the death toll and no official figures have been released by Maduro's government.
Earlier on Tuesday, the United Nations Human Rights Council said 850 people have been detained since January 23, the day Guaidó declared himself president amid anti-government protests.
On January 23, 696 people were detained, the highest number of recorded detentions in Venezuela in 20 years, the United Nations Human Rights Council said.
Guaidó, leader of the opposition and head of the National Assembly, quickly energized the movement against Maduro.
Several nations -- including the United States and Canada -- have officially recognized Guaidó's presidency. Others, including China and Russia, still support Maduro.
The United States announced sanctions against Venezuela's state oil company. Venezuela's military attaché in Washington, Col. José Luis Silva Silva, defected on Saturday, saying he stands with Guaidó in the power struggle.
US national security adviser John Bolton on Sunday warned the Maduro government that violence against Venezuela's political opposition, including Guaidó, would be met with stern reprisals.
Maduro has accused the United States of orchestrating a coup to remove him from the presidency.
Venezuela's top brass have shown unflinching loyalty to Maduro, with their declarations in support of his regime airing in a loop on state television. Defense Minister Vladimir Padrino Lopez has said Venezuelan soldiers would die for their government.
Guaidó on Monday called for massive rallies to demand Maduro's ouster.