There's confusion over visas which could lead to travelers breaking the law, according to immigration police at Pudong International Airport in Shanghai.

A common error concerns the 48-hour non-visa stay in Shanghai.

People must have connecting flight tickets before landing in Shanghai to qualify.

"We are seeing frequent cases in which the travelers think they could land in Shanghai, stay over for no more than 48 hours without visa and buy a ticket to the next country from local agency in the meantime," said Liu Yunye, an immigration police officer with the airport.

"The travelers must already have a connecting flight ticket before landing in Shanghai and the destination of the flights must be in a country different from his own and China."

Shanghai's two international airports are the only channels on Chinese mainland from where qualified nationals could enter the country by the 48-hour visa free policy.

"The violators would be rejected by the immigration authority and would have to cancel the trip and fly back," Liu said.

Another frequent misunderstanding was about "zero visas." The zero visa is issued by for foreigners who have overstayed the allowed period in the country. They could use the zero visa to leave the country legally. The special visa is only valid once for leaving from the country.

But many foreigners have mistaken the zero visa as a legal permit to return to China.

The police say foreigners leaving the country with a zero visa should apply for a new entry visa before travelling back to China.