The number of people reported missing in violence-wracked Mexico has exceeded 100,000, according to official data, with rights groups calling for "immediate" action from the government to locate the disappeared.

The country's National Registry of Missing Persons -- which has been tracking disappearances since 1964 -- said that as of Monday, the whereabouts of 100,012 people are unknown. About 75 percent are men. 

Disappearances have skyrocketed in the wake of mounting drug violence that has rocked the country for 16 years.

The Movement for Our Disappeared warned Monday that the figure was "certainly well below the number" of cases that are reported daily, calling for the government to "deal with this crisis in a comprehensive and immediate manner." 

Last April, the UN Committee against Enforced Disappearances warned that Mexico was facing an "alarming upward trend" in missing people cases.

Organized crime groups were mainly responsible for these disappearances, the UN body said, with "varying degrees of acquiescence or omission" on the part of public officials.

The lack of official help in investigating the cases has led families of the disappeared, especially mothers, to form groups that search for clandestine graves in the hope of finding their relatives.

The Mexican government has reported that around 37,000 unidentified bodies are being held in forensic services, though civil organizations warn the number could be much higher.

Authorities are working to consolidate a database of the disappeared with genetic samples, though many corpses have been buried without being identified due to the country's overflowing morgues.

The UN's top human rights body said the disappearances represented a "human tragedy of enormous proportions."

"No effort should be spared to put an end to these human rights violations and abuses of extraordinary breadth, and to vindicate victims' rights to truth, justice, reparation and guarantees of non-repetition," said UN High Commissioner for Human Rights Michelle Bachelet.

The first reported disappearances in Mexico date back to the authorities' so-called "dirty war" against leftist movements from the 1960s-1980s.

Mexico has also registered over 3
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