Beijing - A European business group on Thursday said it was concerned that China's pre-Olympic toughening of its visa policy could bring "serious problems" to EU firms.

"The introduction of such restrictions without warning creates serious problems for companies operating in China," the European Union Chamber of Commerce in China said in a statement.

The Shanghai Foreign Economic Relations and Trade Commission announced on its website that the granting of business visas for visits to Shanghai would be suspended until mid-September to "ensure a stable, harmonious society during the period of the Olympics."

"The European Chamber is seeking official confirmation that similar restrictions apply in Beijing and other Olympic cities," it said.

It said it had asked the Chinese government to clarify the new restrictions and explain "how they will work in practice and how long they can be expected to remain in force."

Beijing is the main host city of next month's Olympics, while Shanghai and three other cities will also host some events.

Foreign ministry spokesman Liu Jianchao on Thursday confirmed that China had made a "necessary adjustment" to its normal visa policy "to strengthen our security work against potential threats."

Liu said the changes would "not affect people coming to China and engaging in normal work, study or travel."

The government had already enforced some previously lax visa regulations this year, making it more difficult for independent foreign travellers and business people to enter China, and increased checks at hotels and housing complexes.

Many hotels in China's capital have blamed the tougher visa rules for their high vacancy rates in the last two months and fewer bookings than expected for the Olympics, which run from August 8 to August 24. (dpa)