The UN Human Rights Council will investigate alleged human rights violations in Venezuela, including executions, disappearances and torture.
The forum approved sending a fact-finding mission after a resolution was put forward by Venezuela's neighbours and backed by European countries.
Many of the 6,000 deaths in security raids since January 2018 could have been extra-judicial executions, it said.
Venezuela's envoy said the "hostile" text was part of a US-led campaign.
The country is suffering a severe economic and political crisis, and a quarter of its 30 million population need aid, according to the UN.
Some four million people have fled in recent years.