Juliaca (Peru) (AFP) - Demonstrators in Peru blocked roads and held mass funerals on Wednesday for those killed in violent anti-government protests that have gripped the country for weeks, as the United States called for "restraint" on both sides.

The deadly clashes have spread to the tourist city of Cusco, the ancient capital of the Inca Empire, where one protester was killed and more than 20 people, including six police officers, were wounded.

In total, at least 40 people have died in more than a month of demonstrations demanding the resignation of President Dina Boluarte, who took over after the ouster and arrest of her predecessor Pedro Castillo on December 7.

The violence has drawn a rebuke from the United Nations, and a delegation from the Inter-American Commission on Human Rights (IACHR) arrived in the country Wednesday to investigate the protests and accusations of political repression.

On Tuesday, Peru's prosecutor's office said it was opening a genocide investigation against Boluarte and other top officials as a result of the deaths.

The epicenter of the protests has been in the Aymara region of Puno, on the border with Bolivia, where thousands of residents walked the streets of Juliaca with the coffins of 17 civilians who were killed earlier this week. 

Each coffin bore a photograph and was draped in a Peruvian flag. 

"Dina killed me with bullets," read the white coffin of Edgar Huaranca, carried on the shoulders of six family members.

The government has imposed a three-day curfew on the Andean region in a bid to calm the tensions.

On Wednesday, a road blockade extended to eight of the country's 25 regions, officials said.

In Cusco, demonstrators tried to reach the city's airport after mobilizing to demand the president's ouster.

The ombudsman's office said one protester had been killed, identifying him on Twitter as the president of the community of Anansaya Urinsaya Ccollana de Anta, Remo Candia Guevara.

"We demand an immediate investigation to find those responsible for the death and proceed to the respective sanction," it added.

Among the more than 20 wounded in Cusco were six police officers, the health ministry reported. 

In Arequipa, Peru's second city, hundreds also marched against the government, while in Tacna, on the border with Chile, an indefinite strike began, marked by episodes of vandalism.

Human rights probe launched

The regional governments of Puno and Cusco are demanding Boluarte step down as a first step to resolving the crisis.

Puno began an indefinite strike a week ago to demand the resignation of Boluarte, immediate presidential and legislative elections and the convening of a Constituent Assembly.

The IACHR commissioners were received by Boluarte at the Government Palace, the seat of the Peruvian executive. 

"We are going to verify the human rights situation. We regret the loss of human life during the demonstrations," said head of mission Edgar Stuardo Ralon, whose delegation will remain in Peru until January 13.

They will meet with authorities, victims and their relatives in Lima, Ica and Arequipa.

The United States on Wednesday urged restraint and the minimal use of force, and backed an investigation into the dozens of deaths. 

"We recognize the right for peaceful protest and expressing grievances through democratic channels, and call for calm, dialogue and for all parties to exercise restraint and non-violence," a State Department spokesperson said.