China said Tuesday a reporter for Singapore's main English-language newspaper has admitted to spying for a foreign intelligence agency, but his wife said he was arrested after a source gave him documents about purged former Communist Party leader Zhao Ziyang (search), who died this year.

Ching Cheong (search) of The Straits Times was arrested April 22 for investigation on suspicion of spying, the Foreign Ministry said, declining to detail the accusations against the Hong Kong-based journalist.

"Ching Cheong confessed: Following instructions from a foreign intelligence agency, he engaged in intelligence gathering activities in China and received a large spying fee," the ministry said in a statement.

Foreign Ministry spokesman Kong Quan, asked at a news conference for details of what Ching was accused of doing and for which country he was accused of spying, would say only, "We have full evidence to support this case."

The company that publishes the Straits Times expressed confidence in Ching, its chief China correspondent, and shock at the accusation against him, saying he acted with "utmost professionalism."

Ching's wife, Mary Lau, said he was detained in the southern city of Guangzhou after a source gave him what he thought was a manuscript of a book about Zhao.

Lau said in a radio interview broadcast Tuesday that Ching told her he may be held for a long time. "I asked him if it was a matter of years. He said he didn't know. I was very shocked," she said.

Lau said her husband had let down his guard when reporting about China.

"Everyone knows Zhao Ziyang is a sensitive topic. He knows this, but he goes to work every day. I think he's become numb and careless. He never thought he'd come under investigation," she said.

Kong denied that Ching's detention was related to Zhao but wouldn't give any other details.

China has detained a number of foreign-based academics, journalists and businesspeople in recent years on charges of violating its vague laws on official secrets.

The accusations of spying have usually involved Taiwan, which split with China in 1949. Beijing claims the self-ruled island as its own territory and has threatened to attack. The two sides are believe to spy actively on each other.

A Chinese researcher for The New York Times' bureau in Beijing, Zhao Yan, has been held since September on suspicion of revealing unspecified state secrets.

Ching is a Hong Kong resident who carries a British passport and has permanent resident status in Singapore, according to the Singaporean government.

"We are shocked by this new accusation," said a statement by Singapore Press Holdings, which publishes The Straits Times. "We have no cause to doubt that in all the years that Ching Cheong has worked with us, he has conducted himself with the utmost professionalism."

The Singapore Foreign Ministry said Chinese authorities "have not approached us on this and we do not have the full facts of the case."

Ching once worked for the Hong Kong newspaper Wen Wei Po, which has close ties to the mainland government. But he quit along with other colleagues in protest at China's bloody crackdown on the pro-democracy Tiananmen Square protests in 1989.

He and his colleagues then started a new magazine about China called Contemporary, which China allegedly tried to shut down by having Beijing-controlled companies warn potential advertisers not to do business with the magazine.

Another Wen Wei Po reporter, Jiang Weiping (search), has been imprisoned since 2000 in China on charges of obtaining state secrets. His supporters say he was falsely accused after reporting on official corruption.