The caution came after the arrest of Singapore Straits Times journalist Ching Cheong, a Hong Kong citizen, on spying charges reignited international concern over press freedom in China.

Chinese authorities have also filed a new charge of fraud against New York Times researcher Zhao Yan, a Chinese citizen, who has been detained since September for allegedly leaking state secrets to foreign organs.

Foreign ministry spokesman Kong Quan denied their arrests were an indication that China was tightening its control on journalists working for overseas media, but said reporters must abide by the rules or face the consequences.

"What they did was not what their profession should be engaged in," Kong told a regular press briefing, despite neither man having been convicted of any charges.

"Journalists need to abide by professional ethics and abide by law and regulations," he said. "When they have violated law and regulations, they should be pursued according to law.

"They can't enjoy privileges or avoid legal discipline just because they are reporters."

He said journalists rights' to report in China were "fully safeguarded" and added that authorities had always tolerated stories that did not show China in a positive light.

But he stopped short of elaborating on what constituted illegal reporting, saying journalists should look up relevant laws themselves.

Most regulations governing journalists in China are vague.

Rights groups said the arrest of Ching was Beijing's way of warning journalists about challenging its iron-fist rule.

According to a tally by Reporters Without Borders (RWB), there are 32 journalists presently in Chinese prisons, while 64 Internet users have also been jailed for posting their views on the web.

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