The bureau said the state security apparatus had decided to motivate the masses to “gradually build up a steel Great Wall against spies and espionage”.

Any reports that proved unfounded would be tolerated as long as the informer was not deliberately giving false information or trying to harass someone.

“Beijing is the top choice for overseas spy agencies and other hostile forces to conduct activities of infiltration, subversion, division, destruction and information theft,” the bureau said.

The state security apparatus has decided to motivate the masses to “gradually build up a steel Great Wall against spies and espionage”, the statement added.

Raffaello Pantucci, director of international security studies at the Royal United Services Institute in London, said these kinds of offerings were meant to rally the public and grab attention.

“Clearly China wants to be alert to spies, but this also gives the public the sense of having threats from outside that they need to mobilise against,” Pantucci said.

“This will give them the sense that the government needs to be there to be their great protector, but also will focus attention away from other domestic concerns. It also helps justify an increasing security effort at home.”

Veerle Nouwens, a research analyst also from the Royal United Services Institute, said the move pointed to official distrust of foreign entities on the mainland.

Nouwens said overseas intelligence services were likely to be most interested in information on the government, the party, military reform and security policies.

“The fact that this regulation seems to have high rewards for intelligence over foreign espionage in the capital indicates that there is a heightened concern about this in Beijing and the government,” she said.

Beijing has taken a series of steps that it says will bolster security at home, but which critics say amount to a clampdown on civil rights and overseas non-governmental organisations.

Late last month, mainland authorities barred Australia-based academic Feng Chongyi from leaving China. Feng, a Chinese passport holder, was barred from returning to Sydney for eight days until April 1. His lawyers said he was questioned on national security grounds.

Taiwanese NGO worker Li Ming-che was also detained on the mainland for activities that allegedly endangered state security.

In addition, Beijing has demanded that foreign NGOs register with the police rather than civil affairs authorities, as was previously the case. And early last year, state security agencies posted cartoons in public places warning young Chinese women to be wary of dating foreign men because they could be spies.

Shi Yinhong, an international relations expert from Renmin University, said the moves showed Beijing was more serious about national security, but the efforts could have unintended consequences.

“They are not targeting a specific country, but arresting foreign citizens on suspicion of espionage could harm China’s diplomatic relations with other countries,” he said.

Pantucci said the rewards for reporting on foreign spies contrasted with China’s opening up to the world. “When incentives like this are offered, some will seek to take advantage of them. It is possible some people may get caught, but it would be deeply unlikely that it would have much strategic effect,” he said.