David Agren

Special for USA TODAY

IGUALA, Mexico — The recent disappearance of 43 students and the discovery of mass graves containing the remains of 28 charred human bodies offer an alarming reminder that violent crime persists in Mexico.

That's despite the federal government's insistence that the security situation is improving as it attempts to bolster the country's international image.

"There is much more control of information," Erubiel Tirado, security expert at the Iberoamerican University, says of the government strategy since President Enrique Peña Nieto took office nearly two years ago.

DNA tests show the bodies in the graves found near Iguala are not a match for the missing students, federal Attorney General Jesús Murillo Karam said this week.

The discovery increases the death toll in a nation where thousands go missing each year and dozens of clandestine graves are routinely uncovered.

In its annual crime perception survey, the National Geography and Statistics Institute estimated 41,563 crimes per 100,000 residents were committed in 2013, up from about 35,139 in 2012. Among the most frequent offences: street crimes, robbery while riding public transportation and extortion. Peña Nieto insisted early last month that offenses such as homicide, extortion and kidnapping were on the decline.

In the USA, violent and property crimes were estimated at 3,246 per 100,000 inhabitants in 2012, according to the FBI's Uniform Crime reports.

The Mexican report comes months after 22 suspected gang members were killed in a confrontation with soldiers in Tlatlaya. Murillo says some of the suspects were killed with their own weapons. Three soldiers were charged after a person interviewed by the Associated Press said the suspects surrendered before being killed in the town 100 miles west of Mexico City.

This week, protesting students and teachers torched government buildings, including the governor's office, in southern Guerrero state, demanding answers and action in the disappearance of their classmates.

Tuesday, Murillo said police from Iguala and another municipality handed the 43 missing students over to members of the Guerreros Unidos gang, which splintered off from the Beltrán Leyva cartel.

"It's a political crime in which there was possible organized crime participation," says Iguala Councilor Sofia Mendoza, whose common-law husband, Arturo Hernández, was kidnapped with seven colleagues from a left-wing political party and killed 16 months ago. "We will have to see why."

Peña Nieto seldom speaks on security matters, preferring to promote an agenda of recently approved structural changes. He broke his silence in the case of the students' disappearance, appearing on national TV to express outrage and promise an in-depth investigation.

Security and corruption are proving especially problematic in Guerrero, a state south of Mexico City that contains the glitz and glamour of Acapulco coupled with impoverished indigenous populations.

Acapulco was ranked the second-most dangerous city in the world in 2012 with a homicide rate of 142 murders per 100,000 residents, according to the Citizen Council for Public Safety and Criminal Justice, a Mexico City think-tank.

Fed-up farmers and villagers in some parts of the state grabbed guns in early 2013 and formed self-styled community police forces to run off the cartels, who operated openly in spite of an increased military presence.

"The present situation in Guerrero is not a temporary issue, rather a reflection of the progressive and historic deterioration of security conditions over the past months and years," says Francisco Rivas, director of the non-governmental Observatorio Nacional Ciudadano, which tracks crime figures.

Even in the president's home state — Mexico state, a conglomerate of wealthy industrial areas, shabby suburbs and underdeveloped rural regions — the annual crime perceptions survey found 47% of residents said they were victims of a crime last year — far above the national average.

In Iguala, one city official insisted organized crime and violence weren't issues there.

"We have a relatively safe city. We don't have accentuated problems like others parts of the country," said Andrés Guzmán Salgado, a city councilor.

But José Luis Abarca, the mayor of Iguala, is on the lam, accused by authorities of cooperating with organized crime. And Murillo said of the Iguala police force,"I wouldn't call these police, 'police.' I would call them hit men."