At least eight people, including one police officer, have been killed in Zimbabwe, where violent protests are continuing in the capital of Harare for a second day, according to Amnesty.

A further 200 people have been detained, Amnesty added, and a miltary helicopter was seen on Tuesday firing tear gas at demonstrators.

The unrest broke out after the country's government hiked the price of fuel by 150 per cent.

The Zimbabwe Congress of Trade Unions had called for a three-day national shutdown to protest the price hike.

Demonstrators filled the streets of Harare, where they burned tires and blocked a road at a busy intersection.

People run with loot as protests continue in Zimbabwe (AFP/Getty)

Soldiers attempted to disperse the crowd, as confrontations with angry civilians threatened to escalate.

Among Monday's fatalities was a police officer, who was stoned to death by protesters in the city of Bulawayo, a police spokesperson said.

She said that three people had been killed in the protests, a lower figure than that given by activists and human rights groups in Zimbabwe.

Security forces have faced numerous accusations of heavy-handedness. Social media across Zimbabwe, including WhatsApp, Twitter and Facebook, has reportedly been blocked as the unrest continues.

Monica Mutsvangwa, the country's information minister, said she was not aware of an internet shutdown and Zimbabwe's three mobile telecoms firms had no immediate comment on the outage.

Critics have accused Emmerson Mnangagwa of resorting to Mugabe style tactics to control the protests.

"We are suffering. Mnangagwa has failed this country. Enough is enough, we no longer want this," Takura Gomba, a protester in Harare, said.

Amnesty International expressed alarm about reports of protesters being shot by police officers.

“The police must use force only when strictly necessary," Muleya Mwananyanda, Amnesty’s Deputy Director for Southern Africa, said.

"Even then, they must exercise restraint at all times and use the lowest level of force needed. Firearms may only be used as a last resort, and when strictly unavoidable, to protect life.”

“Millions of Zimbabweans are terrified about the knock-on effects that the fuel increases will have on their daily lives, including for food and healthcare.

“The Zimbabwean authorities must ensure that people are able to express their views freely and safely and must promptly investigate in an independent and impartial manner allegations of police shootings of protesters."

The human rights group said that a boy had been shot in the stomach in the suburb of Mbare. A woman in Harare is also believed to have been shot in the face while on her way to work.

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Officials are beginning to engage with the demonstrators and government officials have entered negotiations with union representatives.

Labour Minister Sekai Nzenza also promised that public workers would get a monthly supplement, of between 5 and 23 per cent of their salaries, from January to March.

The opposition and other groups supporting the shutdown urged people to stay indoors rather than engage in street action.