A court in Beijing has sentenced a Hong Kong journalist who was working for a Singapore newspaper to five years in prison on espionage charges. The verdict, issued behind closed doors, has prompted protests from international press freedom groups who accuse the Chinese government of carrying out a campaign to tighten media controls.

Ching Cheong, a reporter for the Straits Times, a Singapore newspaper, was convicted on charges of supplying state secrets to an organization the Chinese government says is linked to Taiwanese intelligence services.

Agents arrested him in southern China's Guangdong province last year, where his wife says he had traveled to get documents related to the late Zhao Ziyang, a Communist Party official who was purged in 1989 for his progressive views.

The Hong Kong Journalists Association was among the first to protest the verdict Thursday. Chairwoman Serenade Woo tells VOA the conviction sends a harsh message to all journalists working in mainland China.

"It will create a chilling effect, no matter if they come from Hong Kong or even from foreign countries because, under China's law, the definition of national secrets is so vague," he said. "So, when the journalists are doing their job on the mainland, they will not know what kind of information is being characterized as national secrets."

Woo says that previously, ethnic Chinese journalists from other countries sometimes felt protected by the fact that they were foreign passport holders who would be less likely to be imprisoned. She said the verdict Thursday is a signal that this may no longer be true.

Ching, although born in mainland China, was a Hong Kong resident and carries a British national passport.

The Straits Times says it has asked the Chinese authorities to show Ching leniency and compassion because he has health problems. The paper's editors also say that the veteran journalist has never "given us cause to question his integrity and professionalism."

China remains the world's leading jailer of journalists, with at least 32 reporters in prison. Free press advocates accuse the government of president Hu Jintao of intensifying a campaign to tighten control of the media.

Ching's conviction comes less than a week after a Chinese court sentenced Zhao Yan, a Chinese researcher for the New York Times newspaper to three years in prison. He was imprisoned despite an international outcry that included protests from the United States government, which called for his immediate release.

Zhao had been accused of espionage, but the charges were dropped and the court convicted him of fraud instead.