German authorities suspect an Iraqi man accused of deliberately ramming his car into several motorcyclists on a Berlin highway was attempting to carry out a terrorist attack.

Six people were injured, with three of them taken to hospital in a serious condition, after the 30-year-old suspect “hunted down” two motorcycles and a scooter on Wednesday night (Australian time).

German police and prosecutors said the man, believed to be an Iraqi citizen born in Baghdad, appears to have acted alone in carrying out a deliberate attack motivated by Islamist ideology.

He was detained on suspicion of three counts of attempted murder and has since been moved to a psychiatric ward as investigators continue to probe his motives.

Comments made by the suspect after his criminal acts suggest a “religious Islamist motivation,” a joint statement from the Berlin police and the public prosecutor’s office said.

Prosecutors’ office spokesman Martin Steltner said it was “strongly suspected” the man had deliberately “hunted down motorcyclists”.

Several German news outlets reported that the man shouted “Allahu akbar,” or “God is great” in Arabic, as he got out of his car.

The Bild and Tagesspiegel local newspapers reported that he also shouted, “Nobody gets closer, or you will all die” before he rolled out a prayer carpet and began praying.

He was then reportedly approached by a police officer who spoke to him in Arabic. The man was pulled away from the car and detained.

There are indications that the man had psychological problems, the statement from the Berlin police and the public prosecutor’s office also said.

It added that investigators so far had not found any hints that the suspect was a member of any terror group.

“A religiously motivated background cannot be excluded,” the statement read.

About 300 people were stuck on a major Berlin highway for hours after the attack and were given support from the German Red Cross, the Berlin fire department tweeted that evening.

Vehicles parked on the closed motorway following several accidents on the city highway A100 in Berlin, Germany. Photo: AAP

Police arrested the suspect at the scene after a device in his car which the man said was dangerous turned out to be a tool box. 

“The fact that the suspect was possibly suffering from psychological problems does not make this issue any easier,” said Berlin’s senator for the interior, Andreas Geisel.

“If personal problems mix with religiously loaded ideas, this can lead to uncontrollable acts — yesterday’s events have shown in a very painful way how vulnerable our society is.”

-with agencies