Zimbabwe was under an internet blackout on Friday after authorities extended a communications ban to cover emails, while the United Nations (UN) urged an end to a security crackdown on civilians triggered by days of deadly protests.

The government has said three people died during demonstrations that broke out on Monday after President Emmerson Mnangagwa raised fuel prices by 150 percent. Lawyers and activists say the toll was much higher and that security forces used violence and carried out mass arrests to quell the unrest.

In Geneva, The UN human rights office called on the government to stop the crackdown and denounced allegations of "generalised intimidation and harassment" of protesters.

As life returned to a semblance of normality in Harare, civilians ventured outside to stock up on food and other supplies while police continued to patrol the streets.

Jacob Mafume, spokesperson for the main Movement for Democratic Change (MDC) opposition party, said he feared the web blackout was a prelude to more violence.

"The total shutdown of the internet is simply to enable crimes against humanity," he told Reuters. "The world must quickly step in to remove this blanket of darkness that has been put on the country."

Authorities have yet to respond to the allegations of a crackdown, but many Zimbabweans believe Mnangagwa is falling back on the tactics of his predecessor Robert Mugabe by using intimidation to crush dissent.

The president has also failed to make good on pre-election pledges to kick-start the ailing economy - beset by high inflation and a currency shortage, and the trigger for this week's protests.

Referring to allegations of night-time door-to-door searches against demonstrators and beatings by police, UN human rights spokesperson Ravina Shamdasani said hospital medics had treated more than 60 people for gunshot wounds.

"This is not way to react to the expression of economic grievances by the population," she said.

One Harare schoolteacher waiting in a fuel station queue said filling his petrol tank twice a month would now cost him $528 rather than $230.

"I will have to probably cut on some other things or simply decide not to drive to work," Gilbert Kepekepe told Reuters.

PASTOR MAWARIRE IN COURT

Activist group Zimbabwe Lawyers for Human Rights said it was representing more than 130 people arrested following the protests.

They include activist pastor Evan Mawarire, who appeared in court on Friday for magistrates to rule if he has a case to answer on charges of subverting the government.

Mawarire, who rose to prominence as a critic of Mugabe and led a national protest in 2016, was tried and acquitted on similar charges in 2017. He faces up to 20 years in jail if convicted.

Mawarire was arrested on Wednesday after encouraging Zimbabweans in social media posts to heed a strike call from unions.

Government officials were not immediately available for comment on the internet blackout, which critics say is an attempt to prevent images of heavy-handedness from being broadcast around the world.

Authorities partly cut off internet access on Tuesday, while Friday's fuller shutdown also affected emails.

Leading mobile operator Econet Wireless said the government had ordered it to shut down services.

"We were served with another directive for total shutdown of the internet until further notice," it said in a statement. "Our lawyers advised that we are required to comply (pending a court ruling)."

Due to the shutdown, Harare banks were providing only partial services and no cash machines were working, a Reuters witness said, while long queues formed at petrol stations and shops.