Officials at Kunming International Airport in China seized suitcases full of Bibles being carried into the country by four American Christians on Sunday.

Pat Klein, Steve Nichols, Forrest Higginbotham and his 15-year-old grandson Stephen Constantinou were carrying around 300 Bibles when they were stopped after flying into Kunming from Thailand.

According to the group, the officials told them that the Bibles were "illegal religious literature", according to China Aid Association, a group that works to support the persecuted church in China.

Klein told AFP by telephone from Kunming, "We've not done anything wrong. We're not trying to overthrow the government or disrupt the Olympics."

The missionaries were planning on distributing the Chinese-language Bibles among pastors in the communist country where it is illegal to sell Bibles in bookshops and the government even limits the number of Bibles available in churches belonging to the state-sanctioned Three Self Patriotic Movement.

"The Chinese leaders keep telling the world the Chinese people have religious freedom. To even prevent them from receiving bibles certainly contradicts that claim," Klein told CAA president, the Rev Bob Fu, over the phone.

Officials told the missionaries they could take one Bible each with them on their visit, but would only be allowed to pick up the remaining Bibles on their way back out of the country.

"I appeal to the Chinese Government to release those confiscated Bibles to the four individuals who deeply care about the Chinese believers," said Rev Fu, "I urge the international Christian community to pray for the four courageous fellow brothers for their safety in China."

China has repeatedly come under fire from rights groups for its persecution of house church members. Persecution watchdogs Open Doors and Release International have rallied supporters to pray for underground believers over the period of the Olympics, fearing that the Games have only triggered greater persecution.

US President George W Bush appealed to China to uphold religious freedom following a visit to a state-sanctioned church in Beijing on the opening weekend of the Olympics. CAA said that underground church leader Hua Huiqi was detained by police whilst on his way to the service before escaping and going into hiding. Chinese police deny the allegations.