At least six people have been killed and 16 others injured in a train accident on a bridge linking Denmark's central islands of Zealand and Funen, according to train operator, Danish Railways (DSB).

The incident on the Great Belt Fixed Link occurred at 8am local time (07:00GMT) on Wednesday with objects from a freight train hitting the passenger train.

Danish media reported that a tarpaulin on a freight train hit the passenger train, which was going in the opposite direction, prompting it to brake violently.

Police spokesman Arne Gram said the passenger train "hit an unknown object", but did not further comment.

Photos from the scene show the freight train was carrying crates of beer, and the tarpaulin that covered the train was torn in pieces.

Kasper Elbjoern, spokesman for Danish brewery group Carlsberg, confirmed that a freight train transporting its cargo was involved in the accident.

Jesper Nielsen, who was on the passenger train, told Denmark's TV2 the train "was out on the bridge when there was a huge 'bang' .... very quickly thereafter, the train braked".

Flemming Jensen, the CEO of state-owned Danish Railways, said police and the Danish Accident Investigation Board are investigating the damages. He said the operator "will contribute everything that we can to the investigations".

The Copenhagen-bound train from Odense city had 131 passengers and three members of staff on board, according to DR, a local broadcaster.

In a statement, police urged passengers to contact next of kin to inform them of their safety and urged people not to share photos and videos of the accident.

The report also said that an accident centre was opened in the nearby town of Nyborg on the Funen side of the bridge, where people involved in the crash could receive help.

Police said the bridge was closed for both trains and vehicles.