A major Danish police operation shut two key road bridges to traffic and halted ferry services to neighbouring Sweden and Germany, effectively isolating the country’s capital, Copenhagen, for several hours.

The Oresund bridge linking Denmark and Sweden, the setting of the Nordic noir series The Bridge, and the Great Belt bridge between the islands of Zealand and Funen later reopened as hundreds of Danish police and soldiers used cars, sniffer dogs and helicopters to hunt for a black Swedish-registered rental car.

The driver and two passengers in the V90 car, a Hertz rental car stolen from Malmö airport, were wanted in connection with “a serious crime”, Danish police said in a statement, adding that anyone who saw the vehicle should “on no account try to make contact with the occupants, but notify the police immediately”.

The ferry terminal at Helsingoer. Crossings to Germany and Sweden have been cancelled. Photograph: Keld Navntoft/EPA

The eastern island of Zealand, where Copenhagen is located, was cut off for about two hours, causing long tailbacks and leaving thousands of travellers stranded around Copenhagen.

Copenhagen’s airport remained open but train traffic to and from the city’s central station was temporarily suspended, while ferry services were slowly recovering and some trains linking western Denmark to Copenhagen skipped some stops to catch up.

The state broadcaster DR said the crime was believed to be a kidnapping, adding that the manhunt had been extended nationwide. The Danish army confirmed it was involved in the search but referred all questions to the police.

“I spent 41 years in the Danish police, I have never seen such a big action taken before,” Hans Jorgen Bonnichsen, former head of operations at the Danish security and intelligence service, told local media.

• This article was amended on 1 October 2018 to correct the spelling of Zealand, from Zeland. In addition, an earlier version referred to the car being sought as “hired from a Hertz agency in Stockholm”. In fact it was a Hertz rental car stolen from Malmö airport.