At least 30 people have been injured after a car drove at “full throttle” into a crowd of mostly children during a carnival parade in west Germany.

Eyewitnesses reported seeing a silver Mercedes swerving around special traffic barriers before ploughing into carnival-goers in what they say appeared to be a targeted attack on children.

The 29-year-old German driver accelerated more than 30 metres into the Rose Monday carnival parade in the town of Volkmarsen on Tuesday morning (Australian time), before coming to a halt.

Police swarmed and dragged him out of the car. Witnesses told German news website Hessenschau the man was still pressing the accelerator even as police approached.

They believe he acted deliberately and injured at least 30 people, seven of whom are in a serious condition. Paramedics set up makeshift medical tents to treat several young kids.

Other local media said the driver broke through plastic barriers set up by police around the parade area, where 1500 people were expected to gather.

News website HNA cited witnesses as saying the car had driven into the crowd “at full throttle”.

Forensic experts investigate next to a silver-coloured Mercedes car that crashed into a group of revelers. Photo: AAP

Police spokesman Henning Hinn said officials are “working on the assumption that it was a deliberate act”.

“There were several dozen injured, among them some seriously and sadly also children,” Ms Hinn said.

Some of the injuries were life-threatening, she added.

Dr Reinhard Kubat, who was at the scene, said: “Crying people came towards me. There were mainly injured children on the street, but also older people.

“Children came up to me and said it did, pop, pop, pop whenever the car ran over a person.”

Local reporter Elmar Schulten said when she arrived at the scene, “15 people on the floor, including many small children”.

Many other children were seen crying in their parents’ arms following the incident, she said.

The alleged driver was taken into custody under police guard after angry locals surrounded the crashed car.

The driver of the car has been arrested. Photo: AAP

Attorney General Alexander Badle said the unidentified man who sustained injuries while ramming into the crowd “was not drunk and cannot be heard because of his injuries”.

The incident comes less than a week after a man gunned down 11 people, including himself, in one of the worst racist attacks in Germany since World War II.

This week, crowds were gathering for a traditional procession ahead of the Christian season of Lent.

Police called off all carnival parades in the German state of Hesse, where Volkmarsen is located, as a precautionary measure, but said they were not aware of any danger elsewhere in Germany.

A joint statement by the General Prosecutor’s Office in Frankfurt and police in the state of Hesse said the motive of the crash was being investigated.

“The investigation – especially on the background of the crime – is ongoing,” the statement said.

“No information can currently be given on the motive in particular; it is determined in all directions.”

German Chancellor Angela Merkel said her thoughts were with the injured and their relatives and thanked police and medics.

-with agencies