At 6:49 a.m. on Oct. 17, not long after the police completed a predawn operation to clear a volatile protest camp in Hong Kong's densely populated Mong Kok neighborhood, someone posted a "call to action" on a popular online forum, urging residents to retake the streets.
"Tonight, if you're a man, let's revive Mong Kok," a user calling himself Li Siu-ming wrote on the HKGolden website. "If there are no other options, we will have to blockade the railway station, paralyze the MTR," he added, referring to the city's subway system.
There was little to distinguish his posts from others online about the pro-democracy demonstrations that have disrupted Hong Kong for more than a month. But the next day, the police demanded user data related to his messages, according to HKGolden's manager.
Several hours later, officers arrested a 23-year-old man at his home, saying he had "incited others on an online forum to join the unlawful assembly in Mong Kok, to charge at police and to paralyze the railways." In announcing the arrest, a police spokesman, Hui Chun-tak, made a sweeping assertion: It is a crime in Hong Kong to post messages calling on people to attend the protests.
"I stress, inciting others to commit criminal acts on the Internet is illegal," he said.
The warning, along with a refusal to disclose more information about the case, has heightened fear that the authorities in this former British colony have begun to police the Internet using methods more often associated with the security forces in mainland China, where web censorship is routine and a crackdown on online dissent has been underway for more than a year.
Hong Kong has enjoyed a high degree of autonomy since its return to Chinese rule in 1997, retaining a Western-style legal system and protections for freedom of speech. But concern about China's growing influence and anxiety that the territory is becoming more like the rest of China have helped fuel protests demanding open elections for the city's next leader.
"The protests are about protecting these Hong Kong values and freedoms from mainland encroachment," said Maya Wang, a Hong Kong-based researcher for Human Rights Watch, adding that the arrest "raises suspicions and questions precisely about these values' being eroded."