(CNN) Nicaragua has instituted a "shoot to kill" policy in dealing with protests that has resulted in an "alarming number of deaths," according to an investigation by Amnesty International.

According to the 34-page report, released Tuesday, the government has violated citizens' human rights and not only used "excessive force in the context of the protests, but possibly carried out extrajudicial executions in conjunction with pro-government armed groups."

Civil unrest has entered its sixth week in Nicaragua as protests continue throughout the country. At least 76 people have been killed, according to the Inter-American Commission on Human Rights, with close to 900 injured in what appears to be the largest protests the country has seen since the civil war ended in 1990.

Human rights lawyer and Amnesty International Director of Americas Erika Guevara-Rosas said the death toll is now at least 83.

The Nicaraguan government has reported 15 dead since the conflict began on April 18 over social security reforms that would increase contributions by workers and employers and reduce retired workers' pensions. The reforms were subsequently reversed by the government, but the unrest has continued.

Protesters are calling for the removal of President Daniel Ortega and "democratization" through reforms in the electoral laws, such as advancing the elections. They also demand justice for the fallen victims, calling for an investigation into the violence.

Fresh clashes between students and armed groups

Multiple social media posts on Monday showed university students clashing with armed groups at the National University of Engineering in Nicaragua, including posts from Guevara-Rosas and Nicaraguan human rights activist Bianca Jagger.

According to a witness statement sent to CNN by one of her associates, Jagger saw the conflict from across the street, witnessing armed groups attacking, followed by anti-riot police "shooting live ammunition with AK-47 assault rifles."

"They were dressed to look as if they were going to war, except that their targets were young unarmed students," Jagger said. "It was a terrifying scene."

Guevara-Rosas said there was a second attack where she also witnessed anti-riot police with heavy weapons beating students and taking them away in pickup trucks.

At Hospital Bautista Nicaragua on Monday night, a person on the phone said there were many injuries but said they were too busy to speak and hung up before providing a name.

Antonia Urrejola, commissioner of the Managua-based Nicaraguan Center for Human Rights, condemned the clashes at the university, calling for an end to the violence.

Heavy police presence was seen Monday morning by a CNN en Español crew on the ground after a radio station, Radio Ya, was set on fire. Rosario Murillo, the country's first lady and vice president, called the incident an "act of hate."

One police officer died after being shot while working to "re-establish public order" in the area of the fire, National Police said Monday, adding that their forces were "attacked by a group of hooded men with firearms, mortars and stones."

State accused of using armed mobs

According to information received by Amnesty, the "Nicaraguan government has used armed individuals or pro-government armed groups that act in collusion with state officials, in particular the National Police, or with their acquiescence or tolerance."

Known as Sandinista turbas (or mobs), these pro-government armed groups dress in attire associating them with the state, some riding on motorcycles, the report said.

Camera footage, images and numerous interviews with family members, hospitals, human rights organizations and others reviewed by Amnesty show these groups were "apparently used by the government to generate disorder, make threats and carry out attacks."

"The authorities have been negligent in their handling of the crisis, in particular President Ortega," Guevara-Rosas said. "People are demanding justice, answers and asking for protection from the security forces but what we are seeing is the opposite: indifference, failure to investigate and to seek justice."

"This discourse of denial, this is the head of the systematic political repression. The divisive rhetoric from the President and vice president is as if these students are small groups inciting violence, but we have witnessed these massive groups protesting. They are not small," she added, speaking about the student movement that has been extremely vocal since the beginning of the unrest.

Messages from CNN to the National Police and the government remain unanswered.

The US Embassy in Managua closed Tuesday in expectation of protests. Embassy personnel were told to avoid the Rotunda Universitaria, the area where all universities are located, because of the "ever-expanding roadblocks and concerns of violence."

Students feel brunt of violence, Amnesty says

UPOLI, the Polytechnic University of Nicaragua, is "one of the areas where the highest number of attacks on protesters in the country were reported," according to the Amnesty report, which added that in the first five days of protests, more than 400 people were injured, around 311 at or near the university, citing the Nicaraguan Red Cross.

Amnesty's investigation concluded that between "19 April and 12 May, 2018, people were arbitrarily deprived of life in the context of the protests and the excessive use of force."

Among the acts Amnesty alleges were taken by authorities: media censorship, obstruction, intimidation, failures to conduct proper forensic examinations, improper evidence management, refusals to take family statements and prevention of investigations.

Amnesty also said authorities are forcing families to sign a document in which they must waive their right to file complaints before the bodies of their loved ones are handed over.

"Based on the pattern identified, a considerable number of casualties could be considered extrajudicial executions," the report said, adding that the deaths happened "with the knowledge of those at the highest level of the Nicaraguan state, including the President."

Report recommends independent investigation

Based on the investigation's findings, Amnesty said it believes the government's strategy was "intended to punish dissenting voices, discourage further public criticism and cover up human rights violations and crimes under international law."

It calls for authorities to respect human rights and the freedom of expression, and demands an independent and impartial group of experts come to the country to investigate the crisis.

"The conditions inside the country do not amount for impartial investigations to take place," Guevara-Rosas said. "The organizations have collapsed."

A national dialogue between the government and various sectors of society has failed to reach an accord. The Catholic Church, which was serving as mediator, left the talks. A commission was set up with three members from the government and three representatives of the protesters to work out an agreement.

Murillo and Nicaraguan Foreign Minister Denis Moncada continue to reaffirm the government's commitment and openness to the dialogue.

Lesther Alemán, a student leader, has said the dialogue isn't for compromise but rather for negotiating Ortega's exit.