An eight-year-old boy has been killed by a train after a 'stranger dressed in dark clothing' pushed him and his mother from a platform in Germany.

Horrified witnesses say they saw the man push the child and his mother, 40, in front of a high speed InterCity Express at Frankfurt's main station at about 10am.

The boy's mother was able to save herself by rolling into a narrow gap between tracks, but she lost hold of her son who was fatally hit by the oncoming train.

Local reports say the man, dressed in black trouser and an olive T-shirt, attempted but failed to push a third victim off the platform at the busy station which witnesses said was full of children at the time.

He tried to run off but was chased and overpowered by passersby before being detained by police, who have opened a murder investigation.

Police say there appears to be no connection between the 40-year-old suspect, thought to be from Eritrea, and the mother and son. The motive for the attack is not yet clear.

An eight-year-old boy has died after he and his mother were 'pushed' in front of an incoming high-speed train at Frankfurt's main station, shortly before 10 this morning. Pictured: Police run onto the tracks following the attack

Horrified witnesses say they saw the man push the child and his mother, 40, in front of an InterCity Express at Frankfurt's main station at about 10am.

The mother is being treated in hospital.

Police told BILD: 'The mother was barely able to save herself. Passersby watched the attack and ran after the fleeing man, of African descent. He was arrested in the station'.

Several witnesses saw a suspect dressed in dark clothes pushing the child, local media reports.

Commuters at the station 'howled' after seeing the child fall to his death, as police, fire brigades, 16 ambulances and a helicopter arrived at the busy station in Germany's financial capital.

Witnesses saw a man dressed in dark clothing push the child and his mother. The mother saw able to save herself, police say. The train is believed to remain on the track after the child was run over (pictured)

A general view of Frankfurt central station after a child on the tracks was run over

Several witnesses needed medical treatment after seeing the death, hessenschau.de reported, and a conductor, who saw the incident from a train, shouted as it was happening.

The station was 'full of children' a witness told the publication. Another, who was on the train, said 'people collapsed howling'.

Four of the busy stations tracks were closed following the attack, causing delays for dozens of commuters.

The ICE train, travelling from Dusseldorf the Munich, is capable of running at speeds of up to 186mph (300kmph).

Several witnesses saw the attack at the busy station in Germany's financial captial

According to news channel NTV, the suspect is a citizen of Eritrea.

Interior Minister Horst Seehofer issued a statement condemning 'this appalling act in the strongest terms' and cautioning against drawing conclusions before more is known.

Seehofer said that in view of 'several serious crimes' recently, he would interrupt his vacation and meet the heads of security authorities Tuesday.

He didn't specify what he was referring to, but Monday's incident followed a case earlier this month in which a 34-year-old woman was pushed in front of a train and killed in Voerde in northern Germany.

The 28-year-old suspect in that case, a German-born Serb, is in custody.