The United States must do its part to halt weapons trafficking and drug use behind some of Mexico's violence and insecurity, the top UN rights official said Friday.

"I do call on the United States of America, indicated as the principal consumer of drugs and supplier of weapon of Mexico, to do something else in order to provide more security to the people of this country," UN High Commissioner for Human Rights Navi Pillay said in Mexico City.

"The magnitude of the challenge is enormous and some of the roots of the problem are beyond the borders of Mexico."

Pillay, who was concluding a visit to Mexico, noted that her office found that 70 percent of guns sold in the US border states of Texas, Arizona and California end up in Mexico.

The South African judge said she was "deeply dismayed by the very high and still increasing levels of criminal violence" in Mexico, where clashes between drug traffickers and security forces have left over 37,000 people dead since December 2006, despite a nationwide police and military clampdown.

During her five-day trip, Pillay met with President Felipe Calderon, as well as state authorities in the southern state of Oaxaca and officials in the capital Mexico City, along with the secretaries of the interior, defense and public security.

The diplomat noted significant progress in Mexico's human rights reform, but called for more, namely highlighting the "precarious situation" of journalists and human rights defenders.

"I am alarmed by the high levels of impunity that prevail in relation to the assaults against journalists," Pillay said, calling for a mechanism to protect journalists and an "urgent" end to criminal impunity.

Mexico is the most dangerous country for media professionals in the Americas, according to the United Nations, which counted 66 journalists killed and 12 missing over the last decade.