A football kicked over a wall, a lightbulb thrown out of a window, a suspiciously unkempt lawn: for East Germany’s secret police, even the most mundane event was recorded as potential proof of the capitalist enemy trying to sabotage life in the socialist republic.

Thirty years after the fall of the Berlin Wall, researchers at the Stasi Records Agency have for the first time systematically analysed the vast photographic archive the surveillance state amassed as a result of its untrammelled paranoia.

The result is a new coffee table book, Der Blick der Staatssicherheit (The Gaze of State Security), with previously unseen photographs that cast a melancholy eye on the absurdity of life behind the Iron Curtain.

They tell the story of three children who caused an incident when they kicked a football over the Berlin Wall on to Soviet soil in May 1978. The children, two girls and a boy from West Berlin, eventually managed to get their ball back, but not before the Stasi had thoroughly documented the ball’s position – “around 25 metres from the border markings” – and photographed the ceremonial return of the offending object.

Three friends from West Berlin. Photograph: Stasi archive

A lightbulb tossed out of a high-rise apartment caused a similar flurry of activity in the town of Suhl on 7 October 1987, after it hit the roof of a vehicle in a motorcade for state apparatchiks. The Stasi suspected “negative enemy forces” were to blame.

Stasi photograph of a lightbulb thrown out of a window. Photograph: Der Blick der Staatssicherheit/Sandstein Verlag

Over the 40-year existence of communist East Germany, the Ministry of State Security built one of the most tightly controlled surveillance regimes in history. The Stasi created a vast web of full-time agents and part-time spies, with some historians calculating that there was one informant for every 6.5 citizens.

The historian Philipp Springer, who spent two and a half years combing through the archive’s more than 2m photographs, said the Stasi’s attention to seemingly mundane detail intensified as technology became more sophisticated and easier to disguise.

“In the 1950s, photography was still a relatively rare technology. But by the 80s cameras were more widely available and the Stasi discovered them as what they called a ‘weapon’. The number of photographs taken grew exponentially.”

Cameras were hidden inside arm casts, shopping bags, books and bras, with the ministry offering incentives for employees who could come up with ingenious solutions.

A Stasi agent demonstrates a camera disguised as an arm cast in East Berlin in 1982. Photograph: Der Blick der Staatssicherheit/Sandstein Verlag

“East Germany’s secret police had a tendency to see the fingerprints of ‘the enemy’ behind every minor event or mishap, so they began to take pictures of even seemingly harmless everyday objects,” Springer said.

Sometimes, the appetite for photographic documentation could backfire. In May 1980, Stasi spies accidentally took photographs of a senior member of their own team leaving and entering a house that had been put under surveillance in Neubrandenburg. It emerged the man had used the same building to maintain an extramarital affair with a colleague in the secret police.

The Stasi official is accidentally photographed as he leaves the flat where he was having an affair. Photograph: Der Blick der Staatssicherheit/Sandstein Verlag

“When you dive into the archive in a non-systematic way, you find all sorts of stories that surprise you,” said Springer. One cache of pictures documented the story of a 19-year-old Soviet soldier who spent four and a half years hiding in a hole in the ground in rural Brandenburg after deserting from his East German barracks. “If Hollywood had made a film about that, I wouldn’t have believed it.”

Another series of photographs shows a young couple from Dresden with a six-month-old child, who had tried to escape to the west in the boot of a car. The baby suffocated during the journey, most likely because of leaked exhaust fumes, the couple were arrested before making it across the border. Unmoved, the Stasi continued to spy on the couple after the tragedy, even getting a photographer to covertly take pictures at their child’s funeral.

“Many of these pictures are now comical in an involuntary way,” said Springer. “But when you come across a picture like this, it really drives home the incredible inhumanity of this surveillance state.”