Airport customs officials in south-western China have seized 300 Bibles from four Americans, saying it was illegal to bring the books into the country, a US missionary among them said.

Pat Klein, who runs a group called Vision Beyond Borders, said customs officials confiscated the Chinese-language Bibles after the group flew into Kunming from Thailand.

The officials were not immediately available for comment and a police official in Kunming said he was not able to confirm the seizure.

Mr Klein, a 46-year-old from Wyoming, said he has brought more than 10,000 Bibles into China over the past 20 years but has never had books seized before.

"We've not done anything wrong," he said by telephone from Kunming. "We're not trying overthrow the government or disrupt the Olympics."

The group of four Americans, which included a 15-year-old boy and his 78-year-old grandfather, were refusing to leave the airport on Sunday night without the books.

Officials told them they could have the Bibles back when the left the country and in the meantime they could take one each with them, Mr Klein said.

"If China's going to say they have freedom of religion, why take our Bibles?" he said.

China's Marxist constitution provides for freedom of religion but in practice the ruling Communist Party restricts independent worship by forcing groups to register.

The Government says China has 15 million Protestants and five million Catholics in official churches.

There are believed to be millions more - including an estimated 10 million Catholics - in "underground" or "family" churches, which refuse to submit to Government regulation.

US President George W Bush attended a church service in Beijing on an Olympic visit to China last week, during which he repeatedly called on China to allow more religious freedom.

- AFP