A video showing a man being beaten by Venezuelan authorities has emerged amid UN denunciation of police brutality in the country.

Venezuelan opposition leader María Corina Machado tweeted the video out to her 3.7 million followers with the caption “All the brutality of the tyranny collapses when faced with the dignity of just one man.”

The video is reported to have been filmed on Thursday in the northern city of Lechería, and shows members of the Venezuelan national guard beating what appears to be a passer-by.

Twitter users commented that the young man being attacked is called Gianni Scovino and suffers from Asperger's syndrome, a form of autism.

The UN Refugee Agency called on the Venezuelan government on Friday to respect the opposition’s right to protest and to not use excessive force against protesters.

"We urge authorities to respect the wishes of those who want to participate in this consultation and to guarantee people's rights to freedom of expression, association, and peaceful assembly,” UN human rights spokeswoman Liz Throssell said.

Anti-government protests have been raging in the country since April, and are expected to escalate on Sunday ahead of a symbolic referendum vote on President Nicolas Maduro’s plan for a new constitution.

The UN Human Rights Office said six to eight million people are expected to take part in the vote.

The government wants to hold its own popular vote on July 30 to create a Constituent Assembly with the power to rewrite the constitution and dismiss elected representatives.

The UN noted that asylum requests have “soared”, with 52,000 already lodged this year compared to 27,000 in 2016.

Most of the asylum requests have been submitted to the United States, Brazil, Argentina, Spain, Uruguay and Mexico according to UNHCR spokesman William Spindler.

About 100 have died and 1,500 injured since the protests started.