BEIJING — China has sent the global gambling industry a message: Be careful when trawling for business there.

A court in Shanghai on Monday sentenced three Australian employees of Crown Resorts to less than a year in prison each for illegally promoting gambling in China. Including the time they have already spent in prison, all three should be released in weeks or months. Thirteen other employees, one Malaysian and 12 Chinese, received similar sentences, the company said.

Crown, based in Australia, said in a news release that the court had sentenced Jason O’Connor, the vice president of its V.I.P. international operations, to 10 months in prison. Two other Australians, Pan Dan and Jerry Xuan, were each sentenced to nine months. They have been in detention since Oct. 14, the company said.

Three more Crown employees were convicted but not fined or sentenced to prison.

Although gambling is illegal in mainland China, many Chinese flock to Macau — a special administrative region under Beijing’s rule but governed by separate laws — as well as places like Australia, Singapore and the Philippines to try their luck. Many casino operators in those places try to lure Chinese high rollers, or big-stakes gamblers, to their properties by enticing them with rides on private jets, haute cuisine and swift visa approvals.