CENIDH is a Managua-based NGO.
The deaths came in the midst of the biggest street protests the country had experienced since the end of the civil war in 1990. Protesters clashed with security forces and various groups of demonstrators clashed.
In the capital, Managua, demonstrators threw stones and set fire to the police when they reacted with tear gas and rubber bullets. Several television stations were blown out of the air when the government tried to stem the turmoil.
Nicaragua's Attorney General Inés Miranda announced on Thursday an investigation into the deaths.
"A responsible and formal investigation has been launched into the following acts: the loss of lives of students, police and civilians, injuries to students, police and civilians, looting and property damage ̵
The riots, mostly led by students, were spurred last week when President Daniel Ortega tried to change the country's social security system. He carried out a controversial reform of the pension reform designed to stop the growing deficit.
The changes increased the contributions of workers and employers to the social security system, but reduced pensioners' pensions.
President Ortega revoked the resolution on Sunday for violent clashes. Peaceful protests continue in Nicaragua as demonstrators are now demanding Ortega's resignation.
11 years in power
Ortega came to power as part of the Sandinista rebels who overthrew the 1979 Somoza dynasty. He fought against the US-backed contras in the 1980s and remained a key ally with Venezuela.
He was elected president for the first time in 1985 and was unsuccessful in 1990, 1996 and 2001. He was re-elected in 2006, 2011 and 2016. 19659002] In the last presidential elections, Ortega was elected vice president by a landslide victory with his wife.
Critics have accused the couple of passing laws in building a political dynasty.
Nicaragua's constitution prohibits re-election for presidents and also blocks candidates who are relatives of the current president from running.
In 2014, he used his power to urge legislators to circumvent deadlines.
International community condemns violence
The Nicaraguan government has been accused of using excessive force against demonstrators and "arbitrarily closing down media on recent protests," said a human rights organization.
"Human Rights Watch received credible reports indicating that police were using excessive force in several places across the country and that pro-government groups were attacking peaceful demonstrators," Human Rights Watch said in a statement.
Both the United States Department of State and the United Nations have condemned violence against demonstrators and called for a peaceful solution.
The United Nations Human Rights Office condemned violence against protesters, whom the Vice President had previously compared with "vampires" "Saturate blood and they believe they will make progress in their political agenda."
Nicaragua "needs to fulfill its international obligations to ensure that people are free to express their rights to freedom of expression and peaceful assembly," said spokeswoman for UN Human Rights Bureau Liz Throssell in a statement.
The State Department issued a statement Monday ordering the removal of government employees and their families. The department also asked travelers to rethink their travel plans to Nicaragua.
CNN's Natalie Gallon, Joe Sterling, Claudia Dominguez, and CNN en Español's Daniel Silva Fernandez contributed to the report.