Two trains have collided head-on on a level crossing north west of Copenhagen, leaving five people critically hurt and 12 others with minor injuries, medical officials say.

The trains were travelling early on Thursday on a line linking the towns of Hillerød and Kagerup in the North Zealand area of north-east Denmark, with a total of 38 people on board, according to police.

Tim Ole Simonsen of the Greater Copenhagen fire department was unable to say what led to the crash but told Danish TV that all the injured had been taken to hospital by air or by ambulance.

Local mayor Trine Egetved said she was deeply shaken by the accident.

Public broadcaster DR showed images of two yellow and grey trains, both with visible damage to the front, facing each other in a wooded area.

Frederiksborg Fire and Rescue said they had been alert to the accident at about 06:30 local time (05:30 BST) on Thursday.

Egetved, who is mayor of the Gribskov municipality, said those with critical injuries had been flown to the National Hospital in Copenhagen.

"The local track is used by many Gribskov residents, workers and students," she wrote on Facebook.

Denmark's Accident Investigation Board arrived at the scene during the morning and Inspector Morten Pedersen of North Zealand police said they would be working together to find out what had happened.

Pedersen told reporters it was far too early to know the cause of the crash.

Rail accidents are rare in Denmark and one expert suggested one of the train drivers had ended up on the wrong line by over-riding a stop signal as the train left a local station. The Gribskov line is not thought to have been updated with an automated safety system.

Trine Egetved told public broadcaster DR that it was shocking that two trains could collide head-on "and we must ensure it never happens again".