The opposition, which controls the legislature, has been sidelined and its leaders are under threat of arrest after organising protests.
Venezuelan security forces have wielded excessive force to suppress protests, killing dozens, and have arbitrarily detained 5,000 people since April, including 1,000 still in custody, the United Nations human rights office said on Tuesday.
It called on the government of President Nicolas Maduro to rein in security forces and investigate alleged abuses, release people arbitrarily detained, and ensure the protection of the ousted Attorney-General Luisa Ortega.
The UN announcement came as Venezuela's Supreme Court ordered the arrest of opposition mayor Ramon Muchacho of the Caracas district of Chacao, which has been the site of intense anti-government protests against President Nicolas Maduro.
TRT World's Sara Firth has this report.
On Friday, Venezuela inaugurated a new legislative superbody that is expected to rewrite the constitution and give vast powers to Maduro's ruling Socialist Party, defying protests and worldwide condemnation that it undermines democratic freedoms.
"We are concerned that the situation in Venezuela is escalating and these human rights violations show no signs of abating," UN human rights spokeswoman Ravina Shamdasani told a news briefing in Geneva.
UN High Commissioner for Human Rights Zeid Ra'ad al Hussein said in a statement: "These violations have occurred amid the breakdown of the rule of law in Venezuela, with constant attacks by the government against the National Assembly and the Attorney-General's Office."
"The responsibility for the human rights violations we are recording lies at the highest levels of government," he added.
The UN human rights office, in preliminary findings based on 135 interviews in Panama and from Geneva in June and July, said it had investigated 124 deaths, and found at least 46 attributable to security forces and 27 to pro-government armed groups, with the rest unclear.
"Witnesses spoke of security forces firing tear gas and buckshot at anti-government protesters without warning. Several of the individuals interviewed said tear gas canisters were used at short range, and marbles, buckshot and nuts and bolts were used as ammunition," Shamdasani said.
Ill-treatment and even torture have been reported in detention, while several hundred demonstrators have been brought before military rather than civilian courts, she said.
"Tactics used included electric shocks, beatings, including with helmets and sticks while handcuffed, hanging detainees by the wrists for long periods, suffocation with gas, and threats of killings – and in some cases threats of sexual violence – against the detainees or their families," she added.
Hunt for rebels
Venezuela's country-wide manhunt continued on Tuesday for the men who assaulted an army base and escaped with weapons after a gunfight with soldiers.
Those who attacked the base near the city of Valencia said their operation was aimed at starting an insurgency against theleftist Maduro.
A group calling itself The Binary Guardians said on Monday it hacked about 40 state web sites. A representative said in an interview that he was a Venezuelan national but declined to give specifics about the group or his location. He said they were not part of Operation David but supported it.
The Trump administration is preparing sanctions against another group of Venezuelan officials linked to President Nicolas Maduro in response to his creation of a new legislative super body in defiance of world condemnation, US officials said on Monday.
The new measures to freeze the individuals' US assets, ban them from travel to the United States and prohibit Americans from doing business with them, could be rolled out as early as this week, one of the administration officials told Reuters.
No final decisions have yet been made on the list of new targets, which is likely to include a significant number of names, or on the exact timing of the announcement, the two officials said, speaking on condition of anonymity.
Washington slapped sanctions on Maduro himself last week following similar action against 13 Venezuelan figures on July 26.
The next round is still expected to stop short of penalties against Venezuela's vital oil sector, considered the toughest of possible sanctions, though such measures, US sources have said, remain under consideration.