The Chinese government said Tuesday that a detained reporter for Singapore's The Straits Times newspaper has admitted to spying for a foreign intelligence agency.

Ching Cheong was detained April 22 for investigation on suspicion of spying, the Foreign Ministry said in a statement.

His wife said earlier that the Hong Kong-based reporter was detained in the nearby mainland city of Guangzhou after a source gave him documents.

"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 Chinese Foreign Ministry said in a written statement.

It didn't give details of what Ching, the Straits Times' chief China correspondent, was accused of doing or say for which agency or foreign government he was accused of spying.

The Straits Times expressed shock at the accusation and confidence in Ching, saying he acted with "utmost professionalism."

Ching's wife, Mary Lau, said he was detained after obtaining what he thought was a manuscript of a book about the purged former Communist Party leader Zhao Ziyang, who died this year.

Lau said in a radio interview aired 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.

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

A Chinese researcher for the New York Times' bureau in Beijing [Images], Zhao Yan, has been held since last 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. As we have stated in our press statements, 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," said The Straits Times statement.

"Until we see incontrovertible evidence, we stand by our belief that he has always acted in the best interests of The Straits Times."

The Singapore Foreign Ministry said late Monday that "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 June 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, 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.

(AP correspondent Min Lee in Hong Kong contributed to this report)

More reports from China