Juan Mendez, U.N. special envoy on torture, and Christof Heyns, special envoy on arbitrary detentions, joined four other envoys in issuing a joint appeal to the Venezuelan government.
They said they welcomed calls by Venezuelan President Nicolas Maduro for a national dialogue, but expressed shock over the reports that 17 people were killed in recent demonstrations and many more were protesters were behind bars.
"The recent violence amid protests in Venezuela need to be urgently and thoroughly investigated, and perpetrators must be held accountable," they said in a statement from Geneva.
National unrest grew out of public frustration with declining economic health in the oil-rich Latin American country. Clashes spilled over into the political arena with Maduro accusing his opponents of getting support from the U.S. government.
The U.N. envoys said they're ready to engage with Venezuelan leaders.
"We call the government to respond positively to pending requests to visit Venezuela, and extend a standing invitation [for a visit]," they said.