Lie on your back and stare directly into the sun – if you shut your eyes or look away, we will stamp on your toes. This is one of the perversely innovative forms of torture allegedly being practised by Burundi’s secret service in the defence of a besieged regime.

Speaking from a safe house, Stephane Gatekh – not his real name – claims that he also had a vice clamped around his leg and was lashed with an electric cable. He was further threatened with bee stings, a machete and having a five-litre bottle tied to his genitals.

Such accounts are increasingly common in the febrile atmosphere that now pervades the capital of this small, landlocked and long-neglected east African nation. Street protests in the capital Bujumbura against President Pierre Nkurunziza resumed last week as demonstrators threw stones at police amid shooting and explosions.

The thud of gunfire can be heard almost every night, while bodies turn up in garbage or gutters almost every morning. Poverty and hunger are rife. And a decade after the end of an ethnic-based civil war, Nkurunziza’s opponents accuse him of playing with fire by trying to turn the Hutu majority against the Tutsi minority.

Gatekh, an artist, says he jogged past a police barrier last month near the spot where Nkurunziza’s feared enforcer, general Adolphe Nshimirimana, had recently been assassinated (a few bouquets of flowers now lie at the busy intersection). It was a misstep that would plunge Gatekh into a week of hell.

Officers said he lived in an anti-government stronghold, claimed his phone contained incriminating WhatsApp messages and suggested that he had come to murder Nshimirimana’s widow. Gatekh tried to run away but was caught by a police motorcyclist who warned him: “If you run again, we’ll shoot at you. We’ll start with your head.”

He was handcuffed and bundled into the back of a pickup truck where officers thrust rifle butts into his face and took his money. Gatekh was taken to a secret service detention centre, beaten again and interrogated about his ethnicity. “I sat down and they took away the handcuffs. The first question they asked was, ‘Are you a Hutu or a Tutsi?’ I said I’m a Tutsi. They said, ‘Ah, now you accept you are Tutsi. Every night there are people shooting at us. We’ll go with you and you have to show us where the guns are.’”

Gatekh alleges that he was beaten with an electrical cable, threatened with beheading and taken to a crowded prison cell where all 10 inmates, including three Rwandans, told him they had been severely beaten and tortured. Two days later it was his turn. He was taken out of the cell and told to lie on the ground and look at the sun: “At 11am it is a shining sun. It hurt my eyes and even my face. When I tried to look away, they stepped on my toes. I was shouting so much that another officer told them to stop.

“He told me, ‘Here’s a deal. We give you a police uniform. We go with you to your area and you show us the guns.’ I replied again, ‘I’m an artist. I don’t know anything you’re talking about. I don’t know how to shoot. I only know how to paint.’ They said they would put me in a small house where I would be stung by bees, or tie a five-litre water bottle to my testicles, or lock me in a small cell with other people where it’s hard to breathe. I was ready to die: if I die, I can’t be hurt any more.”

Facebook Twitter Pinterest Pierre Nkurunziza, Burundi’s president, who is intending to stand for a third term. Photograph: Jean Pierre Harerimana/Reuters

But Gatekh says his family came to the prison and gave him money, allowing him to buy favours from the guards, and a visit by UN human rights inspectors changed the inmates’ fortunes. About 60 finally got their day in court: Gatekh was discharged, but the judge advised him to leave the country for his own safety.

Now in hiding, he is still tormented. “I fear everything coming around this house. If someone knocks on my door, I have to check it’s a friend of mine. I’m traumatised, I have nightmares. I feel there’s a prison guard walking around. But I’m lucky. Innocent people are being tortured and killed. A friend of mine was wrongly accused because he had the same name as a suspect.”

Gatekh’s account chimes with a report by Amnesty International that found evidence of torture by security forces to extract “confessions” and silence dissent. One man said he had been hit with iron bars, had a five-litre container full of sand tied to his testicles until he fainted, then was forced to sit in a shallow pool of battery acid.

This is the fallout of protests that raged in Bujumbura between late April and mid-June against Nkurunziza’s decision to run for a third term, seen by many as unconstitutional and singled out for criticism by Barack Obama in a speech to the African Union. Police were accused of using excessive and lethal force including shooting unarmed protesters as they fled. At least 100 people are thought to have died in the unrest and 200,000 fled to neighbouring countries.

Nkurunziza, a former Hutu rebel leader, won the July poll as expected but a low-level insurgency continues. Police attempting to search neighbourhoods for firearms find some are effectively no-go areas. Last week in Nyakabiga, for example, rocks were lined across streets as makeshift barricades, while more women than men were visible during daytime because the latter sleep in readiness for armed guard duty at night.

A year ago Ngabo Alain – not his real name – was an electrician. Now he carries an AK-47 rifle and three grenades. “The reason we shoot at night is sometimes we see police or militias entering our district, we have to push them back with guns,” he said. “But we have support from some police and military. They give us guns and keep telling us they are waiting for us to go and push.”

Bodies turn up regularly, the activist continued. “We find them in garbage. Yesterday there was a body in the river. Even just now I heard there is another one. It’s becoming so normal to get someone thrown by your home or in your neighbourhood. They are being killed by the government – there is no other explanation. They want to eliminate us one by one so we will stop the protests.”

So far the conflict has been free of an ethnic dimension as Hutu and Tutsi protesters stand side by side. But several interviewed by the Observer accused Nkurunziza’s regime of seeking to reopen old wounds. No one here needs reminding of the 1993-2006 civil war in which Hutu rebels clashed with an army dominated by Tutsis, or the 1994 genocide in neighbouring Rwanda, where 800,000 Tutsis were lost to killings led by a Hutu extremist government.

Alain, a Tutsi, said: “They keep saying this conflict is about ethnicity, even in public speeches. It’s a mission to divide us. But it won’t be easy because we are still working together. Hutus are being killed and Tutsis are being killed. Both sides are being targeted if they are against the president.”

Innocent Muhozi, owner of the independent Radio TV Renaissance, whose building was rocketed in the wake of a failed coup attempt in May, said: “Over the years the independent media had shown the politics of the country had nothing to do with ethnicity. During all those years we’d been building human solidarity around any person in trouble, whether he’s Hutu or Tutsi. We’ve been destroying the ideological basis of the system. That’s why they’re so mad at us.”

Muhozi, 54, who has been reported dead three times, added: “They woke up during those demonstrations, finding young Hutus and young Tutsis saying no, it’s no longer about ethnicity, it’s about something that is wrong.”

Nkurunziza still commands support in rural areas, including thousands of youth militia members. Jean Jacques Nyenimigabo, a senior adviser to the president, denied the allegations of torture and said the unrest is confined to only four districts out of 119 nationwide. “What is happening in Bujumbura is isolated and we’ll soon find a solution,” he insisted. “The Burundian crisis has been exploited politically and the youth have been manipulated and misused. Measures are being taken to make sure the problem is put at an end.”

But civil society and journalists remain under attack. Last month alone, Pierre Claver Mbonimpa, a human rights activist known as “Burundi’s Nelson Mandela”, was shot and injured, while Agence France-Presse reporter Esdras Ndikumana said he was detained and badly beaten by security forces. State-controlled media now monopolise the airwaves.

“There is a desperate attempt to normalise things,” one locally based analyst said. “They want the rest of the world to think everything is back to normal, but this is not the case. It’s now a country of rumours. There is no media and everyone in the know has fled. I don’t think anybody really knows what’s going to happen.”