China has clamped down further on issuing business visas, government officials said Thursday, in the latest expansion of already-tight entry restrictions for next month's Olympic Games.

Beijing has stopped issuing invitation letters needed for visas for businesspeople until late September, unless the visa involves employment or business contracts, an official with the Beijing Municipal Bureau of Commerce said.

"We don't take in applications related to any other general business matters, such as attending conferences, visiting factories and business negotiations. Such applications will not be handled until after Sept. 20," Chen Yu said.

The change began around the beginning of July, he said.

China has tightened its visa rules to keep out foreign activists and foreigners not properly employed in Beijing, but businessmen have also been caught in the net. Authorities do not want a repeat in Beijing of raucous protests that greeted the Olympic torch as it passed through London, Paris and San Francisco earlier in the year.

The visas restrictions are part of a massive security operation to ensure a trouble-free games, in line with its desire to project an image of a modern China. Dissidents have been monitored or even arrested, and migrant workers told to go home.

In Shanghai, the site of some of the Olympic soccer matches, a notice on the Web site of the Shanghai Foreign Economic Relations and Trade Commission said it will not support visas for routine business visits, market research or training until mid-September. Important business visits will be considered, it said, but the length of time will be shortened.

Andrew Work, executive director of the Canadian Chamber of Commerce in Hong Kong, said the latest restriction on business visas will affect business.

"While the Olympics are important, business doesn't stop," he said.

Juergen Weckherlin, a German businessman in Hong Kong, said people were losing money because they cannot make trips that require face-to-face contact. He used to go mainland China four or five times a month to visit garment factories, he said.

"I understand they are very afraid because of some threats in the air, but people like me have a stable visa record and we have never done anything wrong," said Weckherlin, who runs a blog about the rules called The China Visa Blog.

Travel agents in Hong Kong, a major gateway into China, reported in April that the government visa office had declared multiple-entry business visas would not be available from mid-April until mid-October. In the past, such visas were easily obtainable, and businessmen would take regular trips to the mainland to check up on offices or factories.

At the time both the American and European chambers of commerce in Hong Kong sent urgent letters to the Chinese government, raising concerns over the impact on businesses.

"Obviously, this is not great news. Obviously, we prefer to have no restrictions," Kate Pollitt, executive director of the Australian Chamber of Commerce in Shanghai, said.

Richard Choi, the manager of the Canada China Business Council in Shanghai, said he did not think it would affect businesses too much. Such security was natural for any country hosting the Olympic Games, he said.

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Associated Press Writer Cara Anna in Shanghai contributed to this report.