Six people have died in a train accident in storm-force winds on the Great Belt bridge in Denmark, police have said.

Authorities said the accident happened when an express train on the bridge braked suddenly after being hit apparently by flying cargo from a freight train travelling in the opposite direction.

The national accident investigation board has launched an investigation into the crash, which happened as heavy winds from Storm Alfrida battered large parts of Scandinavia, shutting roads and bridges and leaving more than 100,000 households in Sweden without electricity.

Funen police confirmed in a statement that six people had died and a further 16 were wounded in the accident, which happened shortly before 7.35am on the bridge linking Denmark’s central islands, Funen and Zealand. Police and rescue teams were still working at the site, they said.

The Funen police chief, Arne Gram, told a mid-morning press conference an emergency reception centre had been set up in a sports centre in nearby Nyborg at the western end of the bridge, where psychological support was being offered.

Television footage showed one side of front of the passenger train had been ripped open. Police said one of the freight train’s tarpaulins had been torn off and one possibility was that escaping cargo had hit the passenger train, causing “considerable damage”.

The prime minister, Lars Loekke Rasmussen, offered his condolences. “Ordinary Danes on their way to work or heading home from the Christmas holidays have had their lives smashed,” Rasmussen said.

Several Danish bridges – including the Great Belt – were closed to road traffic early on Wednesday because of the storm, although most train services were running normally. Conditions initially made it difficult for emergency services to reach the train, which was carrying 131 passengers and three staff.

“The wind is exceptionally strong and coming in almost straight from the north, blowing straight across the sound and the Great Belt, the meteorologist Henning Gisselø at the Danish meteorological institute told Politiken newspaper.

The accident was the worst on Denmark’s well-developed rail network in 30 years. The 11-mile (18km) Great Belt bridge, hailed as a major engineering achievement when it opened fully in 1998, is part of the complex bridge-and-tunnel, fixed-link system that connects Denmark and Sweden to Germany.

It includes the world’s third-longest suspension bridge, for road traffic only, a tunnel for trains, and a box-girder bridge that carries both trains and cars and is where the accident happened.

The entire structure routinely carries 21,000 train passengers a day as well as more than 27,000 vehicles.