When it was completed in 2000, the £2.1bn Oresund Bridge, which connects Sweden and Denmark, was heralded as a momentous achievement in European transportation. “The bridge's impact will be enormous and the Oresund region will be transformed,” a BBC report on the infrastructure project’s opening proclaimed.

“It links two countries and two cities - Copenhagen and Malmo - turning them effectively into a single multinational metropolis. Their transport systems will be integrated, so commuters can use the same bus or train pass in either place.”

In the early days, the flow of people between the two nations was seamless and plentiful. Economically the region was booming as trade barriers across the European Union came crashing down.

But, a quarter of a century since Queen Margrethe of Denmark and King Carl Gustav of Sweden met halfway along the bridge to officially open the structure, there is a great deal more caution about the movement of people from one nation to the other.

The “single multinational metropolis” is hanging by a thread with the Danes toughening up border security and checking those moving between the two nations.

Crime is the reason for this increased security. Malmo, the Swedish city linked to Copenhagen via the bridge, has been overwhelmed with violent wars between vicious gangs.

Now deemed more dangerous than Baghdad, the city is one of the main places plagued by the skyrocketing bomb attacks and shootings that have transformed Sweden.

In the last couple of years a disturbing new trend has seen Danish gangs import Swedish criminals for their own dreadful deeds. Hiring teenagers to commit atrocious acts of violence on the other side of the bridge.

Last summer, it was revealed there were 25 incidents involving Swedish citizens traveling to Denmark, some of whom were heading there to commit murder and arson, in just five months.

Danish justice minister Peter Hummelgaard laid out the issue in no uncertain terms, commenting: “Criminal groups in Denmark have hired Swedish child soldiers to carry out criminal deeds. What is happening on the other side of Oresund?”

A lot of the crime in Sweden is being driven by organised crime groups whose leaders live in countries like Iraq and Turkey, which led Hummelgaard to also criticise the Swedes' approach to immigration.

“We said that it would end badly if Sweden did not have a balanced migration policy in combination with an adapted justice policy,” he said.

“I know for sure that things have started to happen in Sweden, and I have respect for the fact that they have a longer democratic process.

“But I do not want to hide the fact that Sweden has been warned about this for many years.”

Over the summer, Denmark beefed up border controls with its neighbour in an effort to prevent contract criminals from crossing the border.

However, given the tremendous flow of people back and forth each day, it is not easy for them to identify threats and, according to Danish criminologist Kasper Fisker, the visible deterrent has had little effect.

“You have the political side to it and then when you speak to criminologists it’s a totally different reality,” he told the Express.

“The political side is that; ‘we have to block the bridge and implement enhanced controls’.

“When you ask a guy like me, I say, ‘yeah, but most of these actors [commiting crimes in Denmark] are not known by police. So how are you going to stop them at the bridge?’

“The only way we can reduce this is by solving the problem in Sweden. Help them solve the problem producing this.”

Despite being based in Denmark Fisker finds himself doing exactly that; working on methods of prevention with his Swedish counterparts.

He remains positive about the bridge despite its now becoming a key route for organised crime.

“A lot of s**t comes over that bridge, but also a lot of nice stuff,” he added.

“It's trying to weigh the pros and the cons. We have a lot of commercial interest in that bridge and it brings liberty. A lot of Danes now live in Malmo and go across the bridge every day and vice versa.”