Inside an apartment block in San Salvador beneath the shadow of the volcano that dominates the city skyline, 20 girls aged between 14 and 18 are in hiding, fearing for their lives. Recently deported to the country of their birth from the US by Donald Trump as part of his evolving immigration clampdown, the teenagers are wanted dead by the street gangs that make El Salvador the most homicidal place on Earth.

Survival necessitates drastic measures when the Mara Salvatrucha, or MS-13, or its rival 18th Street gang want you murdered. First, the girls – branded traitors for daring leave El Salvador to set up home in America – are given radical makeovers; new haircuts and new clothes along with sunglasses that are rarely removed. Then they learn to talk differently, walk differently. All trace of their previous existence is erased. Travel is arranged using bulletproof cars with tinted windows. Finally, the safe house is placed on a short-term lease; the slightest intelligence that the gangs have identified its whereabouts and they’re gone.

“The gangs want to kill them because these girls have specific testimony on the gangs, they want to silence them, but also punish them because they dared escape,” said María García, of ISNA,an organisation that runs the secret safe house as part of the elaborate measures required to protect young women in a country controlled by its barbarous gangs.

It is into this maelstrom of violence that the US president intends to deport nearly 200,000 Salvadorans after he outraged the international community last week by announcing he would terminate their temporary protected status, then denounced El Salvador as a “shithole”.

Twenty five years after the accords that ended the country’s ferocious civil conflict, Trump’s deportees will return to the world’s most dangerous country not at war. As with most hostilities, women are routinely caught in the crossfire. Around 10 a day are subjected to violence and sexual assault, with many afraid to speak out. Others are silenced forever. El Salvador ranks among the world’s deadliest countries for women. During 2016, 524 were killed, one in every 5,000, although such figures document only bodies taken to morgues and not those discovered in hidden dumping grounds.

Those inside the safe house are the fortunate ones. Few of those deported from the US or who have fled the gangs are granted such sanctuary in a country devoid of any state or witness protection programme.

“Deportees from the US face being killed or sexual violence. Most girls try to hide from the violence. The problem is that most don’t have a place to go,” said Salvadoran lawyer Laura Morán.

Salvadoran lawyer Laura Moran, 30, who has fought many cases of sexual violence against women. Photograph: Mark Townsend/The Observer

Speaking at a shopping centre with heavy security in San Salvador, Julia, 19, describes how to navigate life on the run from the gangs. The crucial step requires resurfacing in territory controlled by the rival gang.

“It’s because the gangs rarely communicate with each other, the trick is to materialise without suspicion. You should have deleted Facebook, everything about you. You start all over,” she said, intently scanning passers-by.

If successful, prosaic but vital measures are adopted to stay alive. Each time Julia leaves home she carries $2 in change in case a gang member randomly stops her on the street and demands a gift. “Otherwise they will take your cellphone and if you are not carrying your cellphone then they might kill you.”

She never carries ID. If a gang member discovers you are from rival turf they might punish you, again by death. And always scan the footwear of those nearby. Nike Cortez trainers, says Julia, are the preserve of the 18th Street with Adidas Concha worn by MS-13. Yet identifying members is increasingly fraught, amplifying the risk for the girls and women in hiding.

The stereotype of tattoo-smothered thugs is gradually being challenged. Many now wear suits. Some work in government. “I could be talking to one any time. You cannot trust the authorities, the police are also infiltrated with informants,” said Julia.

Walking in San Salvador is dangerous, but public transport is notorious for attacks. The number 44 bus traverses the capital and is among its most important, yet Julia and her friends never use it for fear of robbery or sexual assault.

Also off-limits is wearing shorts, skirts or tight-fitting clothes: Julia and her friends uglify themselves. “You don’t want the gangs to think about you, ever.”

Even so, evading the gangs of El Salvador can seem futile. Boys aged between eight and 12 are recruited as lookouts and patrol street corners, the ojos – eyes – of MS-13 and 18th Street. Girls live in dread of the moment a gang member decides she is his girlfriend. “If they choose you, you cannot say no. If you say no to sex then they will kill you,” said Julia.

Garcia, who has counselled dozens of gang victims, has identified a structural approach to rape. “One girl is chosen by the palabrero (leader) and she is only his, but the other girls can be shared between 20 to 25 gang members. The girls cannot say no, they are forced to have sex.”

On the north side of the city, behind a reinforced iron door and two men with shotguns, Silvia Juárez is one of El Salvador’s most seasoned authorities on the gang brutality faced by thousands of girls and women. As co-ordinator of the violence prevention programme at the Organisation of Salvadoran Women for Peace, Juárez corroborates the reality that consent is dead for many girls and women in the country. “A lot of women have been murdered for saying no, some manage to run away,” she said. At least 1,200 Salvadoran girls and women simply vanish each year. Juárez recently finalised an exhaustive investigation – not published online because it would prompt attacks – based on interviews with women, government officials and, unusually, testimony from 25 gang recruits. “One answer from all the gang members regarded their niña, girlfriends, and greatly concerned us. All said that if their niña say no they have to die.” Other disquieting truths emerged. In some areas suicides among teenage girls is increasing. Rather than be raped, death is preferable.

Across the city, beyond another set of steel gates and armed sentries, Morena Herrera of the activist consortium Colectiva Feminista, says another issue facing Trump’s deportees is impunity. Herrera had just learnt that police had dropped an investigation into a 19-year-old girl abducted from the town of Suchitoto. Reading from a justice ministry report she said the judicial system was failing the country’s women and girls. “The community alerted the police who reached her before she was killed but not before she was raped. Then the prosecutor realised a gang was involved. The case was dropped.” The same outcome had occurred with another crime that had landed recently on Herrera’s desk, a case of “express kidnapping” where a gang member from Cuscatlán had taken and raped a girl repeatedly for several days before returning her to her family. “She is broken,” Herrera said. Lawyers believe that impunity affects 80% of all cases of violence against women.

Despite the unrelenting tide of sexual violence and targeted killing of women and girls, femicide continues to be largely ignored. Salvadoran solicitor Laura Morán, 30, said: “Even in cases where a woman’s breasts are cut off it isn’t classified as femicide. They should be investigated as hate crimes but rarely are.” Despite such attitudes, Morán said police classified 91 femicides in the country during the first quarter of 2017.

Julia, who fears she might be on the run for ever, says the country’s fundamental culture needs to be challenged for change to happen. “We live in a deeply patriarchal system, we’re taught to say yes to men, accept violence and think men are superior. If you are a man you must prove you are strong, aggressive, capable of violence.”

Some women sent back may choose a fresh start in the remote uplands north of Chalatenango, where gang activity is less febrile. Against a backdrop of rainforest, Estrella Alfaro, 28, describes being caught by the US immigration authorities and the anguish of deportation. Alfaro was near Houston, dreaming of a new life removed from El Salvador’s gang violence, when she was arrested as an illegal immigrant in April 2016 and sent home. “They handcuffed my ankles and hands and put me on a plane. I still think of the US.” Another women deportee hiding in the far north is Betty Gálvez, 30, who was working illegally in a Texas warehouse that was raided by police looking for migrants. She was sent back to El Salvador shortly after Trump won the election. “You feel a failure, but here in the mountains I feel safer.”

Betty Galvez, deported from the US and now living in the mountains of northern El Salvador, stands in front of her home. Photograph: Mark Townsend/The Observer

Sixty miles south, in downtown San Salvador, lies the reception centre where the Salvadorans deported by Trump will arrive. The US has been running around eight deportation flights a week. When the Observer visited, a flight holding 40 deportees landed shortly after dawn. At 10am a bus carrying a further 36, many of them unaccompanied minors, arrived from Mexico. Each was handed two pupusas – a thick tortilla – a bottle of pop and a pair of shoelaces. “They are very confused and emotional. Some don’t know what the time is, what day it is,” said David Magana of the country’s resettlement programme. Gangs target the new arrivals. Deportees are often considered wealthy and ripe for extortion.

Many of the teenage girls and young women come back from the US traumatised. But even the 1,500-mile journey there, García said, is treacherous. Most girls set off for the US expecting to be raped by traffickers. “Many have a contraceptive injection that protects them for three months. When they return to Salvador, many have psychological problems, sexual infections, some are pregnant,” she said. And then the hard work starts: protecting them from men who want them dead.

Some names have been changed