China has a new hotline for reporting spies -- but it will cost you to call it.

Amid increased concerns over security and proliferating official suspicion about the motives of foreign powers, Chinese security authorities on Sunday launched a national phone number -- 12339 -- that citizens can use to report activities they suspect may indicate espionage.

The hotline’s launch was timed to coincide with the one-year anniversary of China's new counterespionage law, according to a notice carried in local media on Sunday.

The aim of the service is to "make it more convenient for people and organizations to carry out their legal duties in protecting national security,” the notice said.

One catch: Many of those who tried to call the number, including a few China Real Time staffers, reported getting a message that it didn't exist.

Some searching around on Chinese social media revealed that the number, which was set up by state security officials in the northeastern province of Jilin, requires callers to first dial the area code for the Jilin capital of Changchun.

A man answering the hotline Monday afternoon said he didn't know why the national hotline was not located in a more central city like Beijing or whether the government planned to set up a toll-free version. So far, he said, no one had called to report any suspicious activity.

The man said he couldn't reveal his name. Nor could he say how many people were manning the phones. "I'm afraid that's a secret," he said.

Beijing-based military expert Song Zhongping told the nationalistic Global Times tabloid on Monday that Jilin “is an important place for safeguarding China's national security because the northeastern region is an industrial and military base.” In July, China’s southern province of Hainan opened a similar espionage hotline, which received dozens of tips in its first two months of operation, according to state media.

For those seeking advice on how to spot potential spies, a post of unknown provenance circulating widely on China’s Weibo and WeChat social media platforms Monday offered a few pointers.

It warned the Chinese public to be wary of a range of people including foreign journalists, “some NGO workers” and students with extensive study-abroad experience.

It also advised citizens to be on the lookout for people who engage in suspicious behavior, such as asking others for their opinions on “sensitive” topics and regularly meeting with others to exchange goods or documents.

Among those on the list: “People who frequently make reactionary remarks at academic seminars and business conferences and overstate the good points of foreign countries.”

Critical social media users noted that much of the advice sounded ham-fisted and questioned whether the post was a joke. The man answering the hotline said he hadn't seen the document and didn't know whether it was genuine.

The national spy-reporting number is only the latest telephone service rolled out by China’s hotline-enamored authorities. In recent years, China has set up official hotlines for citizens to tattle on smokers, polluters, corrupt officials and even purveyors of homemade pornography.

--Josh Chin. Follow him on Twitter @joshchin.