SHENYANG - Bullet trains on a high-speed railway line in Northeast China have been forced to slow down seven times over the last three days because of smoking passengers, railway police said Tuesday.

In the most recent incident, a fire alarm was triggered by a smoking passenger on high-speed train D8072 from Liaoning province's capital of Shenyang to the city of Dalian at 9 am Monday, forcing the train to slow from 200 km per hour to 120 km per hour, said a police officer with the Shenyang Railway Public Security Bureau.

The smoker, a 23-year-old Dalian native surnamed Wang, was fined 200 yuan ($32) for violating relevant regulations.

"Smoking is strictly forbidden on high-speed trains, even in the toilets, washing rooms and connecting areas between cars," said the officer. "Smoking can trigger fire alarms or even cause a fire on the train."

Violators may be subject to warnings, fines or administrative detention for disturbing order in public transport facilities, according to the police officer.

The Harbin-Dalian High-Speed Railway, which went into operation on Saturday linking three provinces in Northeast China, is the world's fastest railway in areas with extremely low temperatures. The train's speed can reach up to 350 km per hour.