Media reports said 17 people were injured with four in critical condition following the collision at Gribskov about 40 kilometers (25 miles) north of Copenhagen.

A police statement called it “a serious accident” but a police spokesman told AFP that all passengers had been evacuated from the trains.

“Two trains collided and the police and emergency services are mobilised in large numbers,” the statement said.

The alert was raised at 6:30am, according to police spokesman Tim Simonsen.

“It was a head-on collision and there are injuries among the passengers,” he told AFP, without giving details.

The mayor of Gribskov municipality, Trine Egetved, said on Facebook that some of the injured were taken to hospital by helicopter.

The area was sealed off by police. But media images showed the smashed up front locomotives of the two trains that were between the towns of Hillerod and Kagerup when they collided.

Egetved said she had been “deeply upset and shocked” by the accident.

“This train is used by many residents of Gribskov, workers and students. The emergency services are working tirelessly, and we are trying, at the central level, to get a clear picture of what happened and to ensure that everyone receives the help they need,” she said.

Denmark prides itself on its safety record, but a 2019 train crash left eight dead and 16 injured.

In August last year, an express train hit a farm truck on a crossing killing one person and injuring 27.