People disembark from a ferry after their arrival from the Greek eastern Aegean islands to the Athens' port of Piraeus, on Monday, Jan. 4, 2016.

But the moves have raised new fears that freedom of movement - one of the cornerstones of the European Union - may not survive the refugee crisis.

A temporary fence has already been erected at Copenhagen airport's Kastrup station where trains will be stopped for the mandatory controls to prevent people from trying to slip across the tracks.

In a further attempt to regain control over the flood of people arriving via Denmark, the Swedish parliament last month passed a temporary law making transport companies responsible for ensuring that those arriving via the eight-kilometre (five-mile) Oresund crossing carry valid photo ID.

He told Swedish newspaper Dagens Nyheter that the reason Sweden got overwhelmed last autumn was because Denmark functioned as a "transit country".

The new border controls just introduced by Sweden are a threat to economic growth in Denmark according to the employers' organisation Dansk Arbejdsgiverforening (DA) and Dansk Erhverv, the confederation of Danish enterprise, Børsen reports.

Denmark made the move after Sweden imposed ID checks for rail passengers traveling between the 2.

Schleswig-Holstein governor Torsten Albig said Monday that "the checks could encroach on our good cohabitation in the German-Danish border region and in particular burden commuters".

Any hope of a quick return to a borderless Europe was crushed by the deadly Paris attacks in November, after which France declared a state of emergency and beefed up border controls with neighboring countries.

Politicians in Berlin were anxious what the decision could mean for the future of the Schengen free-movement zone. Most were from Syria, Iraq and Afghanistan.

Sweden has always been seen as welcoming to refugees, but the country's migration minister recently told Parliament: "The system can not cope".

Yes; it's inconvenient for travelers but it's not breaking the rules.

The bridge was also used as a major theme for the 2013 Eurovision Song Contest, which took place in Malmo, as a symbol of the growing connection between Europe's different cultures. The measure will last for six months and could then be continued.

The Swedish border controls will be imposed on the Öresund Bridge, which connects Sweden and Denmark.

Sweden began checking the identities of people traveling to the country from Denmark from midnight. It is still assessing Denmark's decision and has not indicated when that assessment might be complete.

Germany introduced border controls of its own on the Austrian frontier in mid-September and Seibert said those have been successful - "but it is clear to all of us in Europe... that we need an overall European solution".

The crisis underlines structural flaws in the European Union, showing how it has implemented common rules that it just can't enforce once the external pressures become too great, said Karl Lallerstedt, co-founder of Black Market Watch, a Switzerland-based non-profit group focusing on cross-border smuggling. We want to hear from you.

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