Colombia's government resumed negotiations with demonstrators to end more than a month of protests Sunday, as the UN called for an independent investigation after at least 13 people died in clashes in the city of Cali.

President Ivan Duque's team and some of the demonstration representatives resumed talks in Bogota after nearly a week's pause.

But a resolution seemed far off, as the protesters denounced the Duque administration's "complicit silence" in the face of "excessive" use of force by law enforcement.

Rescue workers in the city of Cali on May 28 carry a corpse on a stretcher as protests against the Colombian government entered a second month
Rescue workers in the city of Cali on May 28 carry a corpse on a stretcher as protests against the Colombian government entered a second month AFP / LUIS ROBAYO

The government responded that an agreement could be reached once the blockades choking up the country's transport infrastructure are lifted.

In just over a month of unrest, 59 people have died across Colombia according to official data, with more than 2,300 civilians and uniformed personnel injured.

The NGO Human Rights Watch says it has "credible reports" of at least 63 deaths nationwide.

The crackdown by the armed forces on the anti-government protests has drawn international condemnation, and on Sunday UN rights chief Michelle Bachelet voiced "deep concern" over the ongoing violence.

Anti-government demonstrators take cover during clashes with police in Cali, Colombia, on May 28, 2021
Anti-government demonstrators take cover during clashes with police in Cali, Colombia, on May 28, 2021 AFP / Luis ROBAYO

Clashes in Cali, Colombia's third-largest city and one of the major centers of the protests, pitted police against armed civilians late Friday, leaving 13 dead, according to officials.

Calling for an investigation, Bachelet's office said it had received reports that 14 people had been killed, and that 98 people were injured, 54 of them by firearms.

It added it had been told that armed individuals, including an off-duty judicial police officer, had opened fire on demonstrators, journalists covering the protests, and passers-by.

Demonstrators stand behind makeshift shields during clashes with riot police in the city of Madrid, Colombia, on May 28, 2021 as anti-government protests continued across the country
Demonstrators stand behind makeshift shields during clashes with riot police in the city of Madrid, Colombia, on May 28, 2021 as anti-government protests continued across the country AFP / Juan Pablo Pino

The policeman was subsequently beaten to death by a crowd, it said, and in parts of Cali civilians were seen firing shots at demonstrators as police looked on.

A witness to the troubles in the neighborhood of Melendez on Friday told AFP a group was marking the one-month anniversary of the protests when "shots rang out."

"They started massacring people," said the 22-year-old, who asked not to be named for fear of reprisal, and claimed the shots came from five people in civilian clothes "hiding behind the trees."

A health worker cares for a Covid-19 patient in the intensive care unit of Emilio Ribas Hospital in Sao Paulo, Brazil, on March 17, 2021
A health worker cares for a Covid-19 patient in the intensive care unit of Emilio Ribas Hospital in Sao Paulo, Brazil, on March 17, 2021 AFP / Miguel SCHINCARIOL

"It is essential that all those who are reportedly involved in causing injury or death, including state officials, are subject to prompt, effective, independent, impartial and transparent investigations," Bachelet said in a statement, calling for those responsible to be held accountable.

The police said in a statement it would investigate claims that its members were "permissive with the actions of armed civilians."

In Colombia, the police fall under the command of the military.

Bachelet's office also said it had received information of at least 30 people arrested in Cali since Friday, and highlighted concerns about the whereabouts of some of them.

Colombians protesting against the anti-government blockades were on the streets on Sunday
Colombians protesting against the anti-government blockades were on the streets on Sunday AFP / Juan BARRETO

"The fair trial and due process rights of those detained need to be ensured," the commissioner said.

On Saturday, Duque was booed by a crowd as he appeared in public in Cali.

The president, who was there Friday to Sunday and chaired a security meeting, had ordered more than 1,100 soldiers to be deployed to the western city.

Some in Cali's poorer neighborhoods told AFP the military deployment to their city made them more fearful, not less.

"If something happens we cannot call the police because they are the ones who are killing," said Lina Gallegas, a 31-year-old community activist.

Luis Felipe Vega, a political scientist at Javeriana University, likened the deployment to "putting out a fire with gasoline."

Cali security secretary Carlos Rojas described scenes in the south of the city as "almost an urban war."

In Cali, as across the country, poverty, joblessness, inequality and the fallout from the coronavirus epidemic have sparked widespread anger and resentment.

The protests, which began on April 28, were initially against a proposed tax increase Colombians said would leave them poorer even as they struggled with pandemic-related losses of income.

The proposal was quickly withdrawn, but the protests morphed into a wider denunciation of the government and the armed forces.

Barricades have been kept burning countrywide and blocked dozens of key roads, causing shortages of many products.

According to authorities, some 87 blockades have been set up throughout the country, mainly in the vicinity of Cali.

Duque has deployed 7,000 troops across the country to help clear and patrol the blockaded roads.

Over the weekend white-clad demonstrators took to the streets of Bogota, Medellin and other cities to demand an end to the protests and blockades.

"Today we go out peacefully to demand an end to the strike... all the road closures and blockades are affecting the national economy and are generating more poverty," Bernardo Henao, a 63-year-old lawyer and cattle rancher, told AFP at one of the gatherings.

Colombia is also struggling to contain the coronavirus situation in the country.

On Saturday it reported a record daily coronavirus death toll of 540.