Too many crimes, including torture, disappearances and killings, go uninvestigated in Mexico, which is suffering a "serious crisis of violence and impunity," the Inter-American Human Rights Commission (IACHR) said on Wednesday.
In a new report, the IACHR highlighted repeated failures to get to the bottom of some 27,000 disappearances registered in Mexico as of 2015, as well abuses of power by police and the armed forces in the fight against the country's drug gangs.
The report, which also acknowledged that Mexico has made progress on judicial reforms, followed a government announcement this week about the deaths of five young Mexicans targeted by suspected gang henchmen.
Their remains were ground up after they were mistaken for members of a rival cartel in the eastern state of Veracruz.
The Mexican government criticized the IACHR report, arguing it did not reflect the "general situation" in the country.
IACHR experts last year condemned the government's account of the 2014 disappearance of 43 trainee teachers in the southwestern city of Iguala, a crime that sparked outrage and battered President Enrique Pena Nieto's reputation.
Pena Nieto has pledged to tackle longstanding failings of the Mexican justice system, but the IACHR report said "the state's response is still insufficient to deal with this serious crisis of violence and impunity."
"Unfortunately, there's a gap between what the law says and the reality. Somebody needs to take responsibility for changing the practices," said IACHR commissioner James Cavallaro, adding the commission was shocked by the impunity it found in Mexico.
"It's like there was no interest in looking for the perpetrators and solving the crimes," he said.
In a statement, the government denied there was a "human rights crisis" in Mexico. It said the report was based on premises and assessments the administration did not agree with.
Furthermore, the government argued the IACHR's findings were not objective or well founded.
"The Mexican state is constantly working to deal with the causes and consequences of violence in the country caused by crime, to guarantee security, to protect, promote, respect and guarantee human rights and improve access to justice," it said.
More than 120,000 people have been killed in drug-related violence in Mexico since former President Felipe Calderon sent in the army to take on the gangs in late 2006.
As the gangs fragmented, many increasingly focused on extortion, kidnapping and human trafficking.