Foreign citizens have complained about complicated new rules needed to apply for a trip to China, citing additional documents such as invitation letters.

Effective on August 1, visitors from the US are required to provide invitation letters issued by "authorized" Chinese agencies when applying for tourist or business visas, according to a recent notice on the website of the Chinese embassy in the US.

The invitation letter should include invitees' personal information such as name, gender, date of birth, tourist destinations, arrival and departure dates and relationship with the inviter, according to the statement dated July 17.

American residents have complained that it is unclear what constitutes an authorized agency, and some tourists were in despair after filling out visa application forms in July and only receiving the required documents a month later, the Los Angeles Times reported.

Similar visa requirements were posted on the Chinese embassies' websites in other countries earlier, including Japan late last year and Britain earlier this year.

When the Chinese embassy in Canada issued the new rules in May, a large number of Chinese Canadians protested that the additional documents had created much more inconvenience for those seeking to visit relatives in China.

"Many tourists, especially individual foreign travelers, will possibly change their destination as they feel it is inconvenient to find an authorized travel agency or individual to provide an invitation letter," Wang Yi, from Topline Travel International Company, told the Global Times.

Wang said the travel agency has sent an increasing number of invitations to tourists in European countries in the last two months. The majority of them complained about the complicated procedure involved in getting a tourist visa to China.

Some even started to speculate about the government's intent behind the new visa policy.

"It is obviously aimed at limiting the number of entries while at the same time gaining more control over which types of visitors are granted entrance," 29-year-old Michael Malley, a US citizen in China, told the Global Times.

Beijing launched a 100-day crackdown against foreigners who try to enter, stay or work in China illegally since May.

More than 50 million foreigners arrived and left China in 2010, 2.33 times as many as 10 years ago.

China passed the law on the entry and exit of personnel in June, which requires foreigners to provide an invitation letter to apply for a tourist visa in 1China. The law is scheduled to be implemented on July 1, 2013.

Some believe the earlier implementation of the visa rules may be related to the upcoming 18th CPC National Congress.

"The tightening of the visa policy is a tool for the Chinese government to maintain stability ahead of the 18th Party Congress," said Wang Xingbin, a tourism professor from Beijing International Studies University, adding that it might hurt tourism in China.