Two who escaped death in the attack on students in Guerrero last September testify to the murderous role of state forces

Uriel Alonso Solís is an affable 19-year-old, the oldest of five children from a poor campesino family. But his grittiness shows through as he recounts the terrible night his college friends – four of whom he grew up with – were seized and hauled off to face a brutal fate that still reverberates across Mexican society.

Alonso survived the horrific attack on unarmed students by state and criminal forces last September in the southern state of Guerrero, which left six people dead, 25 injured and 43 trainee teachers forcibly disappeared.

“Five carloads of masked police surrounded our three buses, and as we got out to see what they wanted they started shooting. There were bullets flying everywhere, and people started running. I saw one of my classmates go down. He’d been shot in the head, everyone was crying and screaming, but I was really surprised how calm I was. I started calling friends at the school to help us.”

Alonso was among those who managed to hide as dozens of his classmates were forced into police trucks and driven away. “I thought they would beat them, but that we’d get them back the next day. We hadn’t done anything, we were just students going to a protest.”

Omar García, 24, another survivor, was among the students Alonso called when the ambush happened. He rushed to the scene where, he says, “we started collecting evidence like bullet casings, and calling the local media. We felt calmer when they arrived, as we thought nothing would happen in front of journalists. But around midnight the police started firing again, directly at us as we tried to run away.” García helped carry one of the injured to a nearby private health clinic. “There were no doctors, but soon two trucks of soldiers arrived from the 27th infantry battalion, which has a base close by. They started accusing us of criminality and violence, as if we were combatants, not students.”

Even with the toxic mix of violence, impunity, organised crime and corruption that has left more than 100,000 people dead and almost 30,000 disappeared since 2006, the bloody events of that night have shaken Mexico to its core. Hundreds of thousands have taken to the streets demanding the resignation of President Enrique Peña Nieto. It is the worst human rights crisis facing Mexico since the 1968 massacre of unarmed students at Tlatelolco, according to Human Rights Watch.

So far, 97 people have been arrested for involvement in the attacks, including police officers, members of the Guerreros Unidos (United Warriors) cartel, and a local mayor and his wife. But the government rejects claims – by survivors, relatives of the missing students, journalists and researchers – that the army and federal officers were also involved.

Earlier this month García suffered a serious blow to his left eye while trying to force his way into one of the local army bases to search for clues. He does not believe the federal attorney general, who insists that all 43 of the missing students were killed and their bodies burned on a rubbish dump that same night, by assassins from the Guerreros Unido criminal gang working for the mayor and his wife.

Facebook Twitter Pinterest Omar Garcia, 24 was called to the scene by Alonso and collected evidence. Photograph: Ginnette Riquelme/Observer

García says they have evidence to suggest that the mobile phone of at least one of the missing students was used in the 27th infantry battalion base. “The army has been linked to organised crime groups in Guerrero and other states for many years, we are absolutely sure they knew what was going on. They didn’t take them, but they enabled it to happen.” He added: “Our history shows us that it is the state who ‘disappears’ community leaders and activists, and that’s what happened on 26 September.”

The attacks were targeted at students from the Ayotzinapa rural school – one of 16 teacher training colleges that came out of the Mexican revolution. These schools are bastions of leftwing politics, which over the past two decades have been increasingly neglected and regarded as breeding grounds for guerrillas and nonconformists by the state.

García is one of 16 children, and most of his siblings are undocumented migrants in the US. Three of the missing young men are from his village. “Our stories are very similar, our parents are campesinos, we all grew up together and the school provided us with the only opportunity to study.”

The case continues to damage Peña Nieto, who has four years left of his presidency, as public outrage across the world – including several protests during a recent visit to the White House – show no signs of abating. A seemingly never-ending run of bad news keeps stoking the political flames. Claims of a new corruption scandal emerged last week involving a property reported to have been purchased by the Nieto family during his time as governor of the federal state of Mexico, from a company which allegedly later won lucrative government contracts. In Guerrero, dozens of clandestine graves have been discovered since September, and prosecutors have linked local police to at least 100 disappearances in the past two years.

Still, politics and business must go on. In the first week of March, Peña Nieto and his wife will make an official state visit to the UK, meeting David Cameron, the Queen, and businessmen as part of a year of events to boost trade, science and cultural links between the two countries.

The coalition government has targeted Mexico as a springboard into the Latin American market, sending several high-level delegations, including deputy prime minister Nick Clegg, Prince Andrew, Duke of York, and most recently Prince Charles and Camilla, Duchess of Cornwall, in an attempt to double bilateral trade to £4.2bn by 2015. Energy reforms passed last year mean the big prize is now Mexican oil, with British companies among those eyeing lucrative deep-sea exploration contracts. In contrast, it is 10 months since it supported a human rights project in Mexico – though Britain is considering providing financial support to local free-speech organisations.

García said: “It is hypocritical for Great Britain to talk about human rights while signing new deals and accepting the president’s word about what goes in Mexico. Mexico is an inferno, and I call on the [British] people who want to show solidarity with us to make some noise in front of Peña Nieto.”

Duncan Taylor, the British ambassador to Mexico, told the Observer that promoting and protecting human rights was a key priority for the British government, discussed regularly with the Mexican government as part of a “positive bilateral relationship”. He added: “… it is right that the international community should be concerned by allegations of human rights abuses, in Mexico as elsewhere.”

On Monday, hundreds of thousands of people across the world are expected to take to the streets to mark the four-month anniversary of the disappearances. So far, only one of the missing students, Alexander Mora Venancio, 21, has been confirmed dead by an independent forensic examination.

Austrian scientists last week said they had been unable to recover sufficient DNA from 16 charred remains, said by the attorney general to be those of the students, to make any positive matches. Friends and relatives of the missing 42 remain hopeful that they are still alive.

After the attacks, Solís was hauled home by terrified relatives, but he refused to quit school or stop searching. “I am the eldest grandchild and my grandmother keeps crying, she’s scared, she wants me home. But it could have easily been me taken that night, and if it had been I think my friends would be looking for me right now … I am not scared, none of us are scared any more.”