A man threatened an attack on a high-speed train in western Germany and lightly injured 12 passengers with firecrackers before being taken into custody in the town of Siegburg near Bonn, police said.

The 20-year-old threw pyrotechnic objects filled with plastic pellets on board an Intercity Express (ICE) train travelling from Cologne to Frankfurt on Thursday evening, a police spokesman told dpa, citing witness statements.

The spokesman said some passengers suffered acoustic trauma. Earlier, a police spokeswoman said some also had minor skin injuries. Most of the passengers escaped with a fright.

The man had threatened an attack and had a knife in his backpack, the police spokeswoman said, without giving further details. The motive was still under investigation.

A spokeswoman for rail operator Deutsche Bahn said possible gunshots had been reported on ICE 19 at Siegburg station at 8:55 pm (1855 GMT). Police later determined that the sounds had been caused by ignited fireworks-like devices. Police described them as so-called airsoft firecrackers, although it remained unclear exactly what kind of devices they were.

According to the police spokesman, the suspect first ignited the devices and then retreated to a train toilet. A passenger locked him inside until the train arrived at the station. The man was then pulled out by police and is now in the custody of Siegburg police, the spokesman said. The Koelner Stadt-Anzeiger newspaper reported that the person was masked.

Around 150 passengers were on board and had to leave the train, where they were attended to by the fire brigade. Many of them were holiday travellers shortly before Easter and stood on the platform with their suitcases, according to police. The train was being fully searched as a precaution and was to remain at the platform in the meantime.