Government security forces in Venezuela are carrying out unjustified killings without any apparent consequences as the rule of law in the country quickly vanishes, according to the United Nations.

A report from the Office of the UN High Commissioner for Human Rights said Venezuelan officers accused in some 500 questionable killings appeared to be evading any charges.

That is a sign that checks and balances have been chiselled away, leaving state authorities unaccountable, high commissioner Zeid Ra'ad Al Hussein said.

The UN report highlighted a case from early this year in which rebel police officer Oscar Perez and six in his group were shot to death as they tried to surrender.

Oscar Perez posted a farewell message to supporters and his family on Instagram shortly before his death. ( Instagram: oscarperezvg )

UN officials say they believe the group was killed on orders from top government officials, in violation of their basic rights.

"The rule of law is virtually absent in Venezuela," Mr Zeid said in the report.

"The impunity must end."

Venezuela rejected the UN report as a "grotesque media farce", saying it omitted information officials in Caracas provided to investigators.

The findings were part of an international push against Venezuela led by officials in Washington, the ministry said.

"Venezuela reiterates its unrelenting commitment to human rights set out in Venezuela's Constitution and international treaties," officials in Caracas said in a statement.

However, UN secretary-general Antonio Guterres "believes that the numbers are truly shocking," deputy spokesman Farhan Haq said later on Friday at UN headquarters.

He said Mr Guterres felt the report "attests to the need for political dialogue and a fully inclusive political solution" to the problems roiling Venezuela.

Rebel cop had launched attack using stolen helicopter

Sorry, this video has expired Grenades were launched at Venezuela's Supreme Court in downtown Caracas from a helicopter.

The report shed light on the death of Mr Perez, who was killed in January when government forces hunted his group down to a mountain hideout outside Caracas.

He had been Venezuela's most-wanted fugitive after attacking government buildings in a stolen police helicopter.

The report said 400 officers armed with assault rifles and an anti-tank rocket-propelled grenade launcher surrounded Mr Perez, who was seen on video calling to surrender.

Police later recovered four rifles, a pistol and two hand grenades from the hideout.

UN officials said their investigation led them to believe that officials who reported directly to socialist President Nicolas Maduro killed the seven rebels in violation of their human rights, and then destroyed evidence.

Venezuela a country in crisis

Venezuela is in the grips of a deepening political and economic crisis marked by food and medicine shortages and soaring inflation that has driven thousands to flee the country in search of a better life.

The country's government has drawn international condemnation since last year, when officials loyal to Mr Maduro formed a constitutional assembly, robbing power from the democratically-elected congress, which is controlled by the opposition.

The UN report looked at cases of excessive government force seen beyond violent street protests and also cites examples of officials threatening or detaining health care workers for shedding light on the lack of medicine and poor conditions.

The report concluded that between 2015 and 2017, some 357 officers were placed under investigation stemming from 505 killings during supposed neighbourhood raids.

But Venezuela's attorney-general, who was critical of Mr Maduro, was replaced last August, and no more information about the prosecutions had been made public, the report said.

It added that evidence appeared to have vanished from case files.

"The state appears neither able nor willing to prosecute serious human rights violations," Mr Zeid said, suggesting the International Criminal Court play a deeper role.

Venezuelan officials did not allow UN officials into the country to compile the report.

Investigators gathered information remotely and included interviews with victims, witnesses, lawyers and doctors.

AP/ABC