China's new travel rules can stop people leaving for up to 3 years

China has new rules about travel in and out of the country. The rules started on Tuesday. They let the government stop a Chinese citizen from leaving China for six months to three years.

Why can a person be stopped? If the government thinks the person did something against China's national security, the person cannot leave. The same happens if the person is thought to have broken rules about technology, including artificial intelligence. Artificial intelligence means computer programs that can learn and make decisions. A person who did something criminal in another country can also be stopped after coming back to China.

Foreign visitors face new rules too. If a visitor writes something false in a visa application, China can refuse to let that person in for up to five years.

Exit bans are not new in China. A court database had 89 records about exit bans in 2016, and 188,760 records last year. This shows that many more people are stopped now.

Some people say the rules are not clear. Chong Ja Ian, an analyst in Singapore, told AFP that the ideas of security and crime are not explained well, so the government can change them easily. China says the rules do not stop ordinary people from travelling. Chinese officials did not answer questions from the BBC.