SAN SALVADOR, El Salvador - Every day, as she travels to the food stall she operates, Mirna Isabel Villalta crosses an invisible but dangerous boundary.

Her modest home is in a part of San Salvador controlled by the Mara Salvatrucha, a gang so ruthless and sprawling that the Obama administration has labeled it an international criminal organization. Her food stall is in the city center in an area controlled by Barrio 18, a gang that despises the Mara Salvatrucha.

She knows she's breaking an unspoken rule.

"You can't go from one barrio to the other," Villalta said. But she does. Every day. And she keeps mum to those around her food stall about where she lives.

"They don't know we live in Mara Salvatrucha territory," she said.

El Salvador's capital _ and indeed nearly the entire country _ is a checkerboard in which gang territories circumscribe the movement of those in the lower economic rungs of society, and especially young men. When a family lives in an area dominated by one gang, it avoids going to an area controlled by a rival gang.

"The control the gangs hold over their territories has never been so complete. It is without precedent," said Carlos E. Ponce, a criminologist and former adviser to the National Civilian Police.

As the gangs deepen connections with regional organized-crime groups involved in drug, weapons and human trafficking, they present a direct challenge to state control over the tiny Central American nation, Ponce said.

The chaos also provides an incentive for Salvadorans to try to flee north for the safety of the United States. Experts trying to explain the huge increase in children and teens who've arrived in the United States say anecdotal evidence points at least in part to the hold that criminal gangs have in El Salvador, Honduras and Guatemala.

As insecurity extends across El Salvador, gang bosses reach for younger and younger kids to fill their ranks.

"Youngsters don't get in at age 14. They get in at age 10 now," said Luis Romero, the head of a project called Homies Unidos that pulls gang members off the streets to give them skills. "You should see the juvenile jails. They are packed."

In Ilopango, a poor sprawling district southeast of the capital, the local government has set up programs to offer training to young people in driving and speaking English. But district authorities have found they have to duplicate some programs, one for areas controlled by the Mara Salvatrucha and another for Barrio 18 areas.

"We've set up soccer schools in each of their territories," said Rosemberg Hernandez, who's in charge of youth programs in Ilopango. "We do this to avoid problems."

Hernandez said the two gangs had different clothing and hairstyles, even different vocabularies.

"It sounds ridiculous but there are things that Mara Salvatrucha gang members won't say. They never say eight or 18," he said, for fear of referring to the rival gang.

While flight to the United States might be one way people are trying to escape the violence, there's an ironic symmetry: El Salvador's gang problem has its genesis in the United States, from the time of the country's civil war, which also sent tens of thousands of Salvadorans fleeing to the United States.

For young people, that war _ which wracked El Salvador from 1980 to 1992 and left at least 75,000 civilians dead _ is ancient history. But by the time peace accords were signed, the gangs were on the rise, formed by gang members who'd been deported from Los Angeles.

"Those kids 18 and 20 years old who joined the gangs have now grown up," said Ilopango Mayor Salvador Ruano. "We've now had at least three generations of gang members."

Salvadoran leaders have tried different tactics to rein in the gangs, beginning with a 2003 program, known as "Strong Hand" and followed by "Super Strong Hand" years later, that swept thousands of gang members into prisons.

"The 'Strong Hand' program only attacked the gang members who were on the street. It filled the jails. But it didn't touch the leaders," Ponce said.

In 2012, the government _ with the help of the Organization of American States _ brokered a truce between leaders of the two gangs that edged the nation's homicide rate down from 12 killings a day to around five. But that truce fell apart earlier this year and homicides are back up. One recent weekend tallied 31 violent deaths.

Now the citizenry widely ridicules the truce.

"Most people say it didn't do any good. They feel it was a nonaggression pact between leaders of the two gangs but that ordinary civilians still paid the price," said Monica Pacheco, the coordinator of a Roman Catholic human-rights observatory based in San Salvador's working-class Mejicanos district.

In Mejicanos, she said, residents "voice a lot of fear about going to another district because they might be tagged as belonging to the rival group. This is something they deal with all the time. It's a life of fear and anguish."

One former Mara Salvatrucha member, Marvin Gonzalez, who spent 10 years in prison for murder and has been free since 2012, said reconciliation between rival gangs was a monumental task.

"For the older ones, there is no forgiveness," he said. "To come to an understanding with someone who's shot your best friend, who's shot at you, to sit down with them, believe me, it's not easy."

Even if gang violence were to diminish, for people such as Mirna Villalta the suffering will go on.

Two years ago, Villalta's 13-year-old daughter disappeared on the way home from school. Two days later, the girl's body turned up on the banks of the Acelhuate River. Members of the local Mara Salvatrucha branch called Villalta afterward and told her "not to denounce the murder of my daughter to the police," she said. "I didn't make the report."

The police and prosecutors got involved anyway, and several gang members are in prison for involvement in the murder.

Villalta has sons aged 10 and 13, and she fears that the gang will force them to join. One day, her 10-year-old disappeared from behind her food stall. He was gone for nearly half a day. Witnesses said a woman led him to a taxi. The boy stepped out of a taxi near her home late that night.

Her boy, she said, "won't say anything about what happened."

She and social workers suspect that gang members took him to frighten him into joining.

Villalta is now working with a lawyer and seeking humanitarian asylum in Sweden. It's been granted, and all she needs is the airfare, said lawyer Karla Salas.