TAIPEI (AFP) - Taiwanese police arrested 19 people for threatening copycat attacks following a stabbing spree aboard a Taipei subway train, an unprecedented attack which sparked panic among commuters, officials said on Monday.
Cheng Chieh, a 21-year-old knife-wielding attacker, killed four people and wounded nearly two dozen others last Wednesday in the first fatal attack on the city's subway system since it began operations in 1996.
Police arrested 19 people across the island for threatening similar attacks in comments posted online, according to the Criminal Investigation Bureau.
Among the cases was a college student surnamed Chan, who said on Facebook: "What Cheng Chieh did on the Pannan line, I'll do the Tamshui line."
Chan admitted to the "emotional" posting but told police that he meant no harm.
However, police justified the "preventive" arrests.
Last Wednesday's attack has cast a shadow on the hundreds of thousands of commuters, prompting security officials to beef up patrols on the busy subway system.
"What the police authorities are doing is reasonable. They could stop the likely imitation of criminal behaviour often seen in the wake of major crimes in the world," said Mr Liao You-lu, the head of the criminal investigations department at National Police University.
All the suspects have been released on bail or are facing further questioning, the Criminal Investigation Bureau said.