A Chinese pastor who has defended churches facing demolition has been arrested along with his wife and son, campaigners say.

Wen Xiaowu, who leads a house church in Wenzhou, Zhejiang province, on China's eastern coast, and his family were criminally detained on April 26. They are accused of "gathering a crowd to disturb social order" and "obstruction of public service", China Aid said.

The human rights organisation said relatives believe these are trumped up charges.

In a statement, China Aid said: "Family members believe... the real reason for the arrests is most probably because of their contacts/meetings with US Consulate officials in Shanghai.

"Pastor Wen has been very active in legal defence work for the churches in Zhejiang during the forced cross demolition campaign in the last three years."

The organisation branded Wen's arrest "a very disturbing chilling development", and likened it to the case of Christian human rights lawyer Zhang Kai, who was released after seven months detention in 'black jail' in March.

Zhang had represented more than 100 churches fighting orders to remove their crosses.

Wen, his wife and their son have not been allowed to see any relatives, and have had their computers and other items confiscated.

They had apparently briefed foreign journalists about the forced cross demolition campaign in Zhejiang.

The Communist Party is believed to be becoming progressively more suspicious of the influence of Christianity, which is experiencing significant growth in China. Up to 1,700 churches have been demolished or had their crosses removed in Zhejiang in the past two years.

Wenzhou is dubbed the "Jerusalem of the East" for reportedly having the largest Christian community in China. 

"To arrest Pastor Wen and his family members (for normal meetings) is a direct slap of face to the US government and American people. He is a man with integrity and passion who is always ready to help others," said Bob Fu, founder and president of China Aid.

"Despite of constant threat against him and his family in the past few years by state security agents, for the sake of rule of law and religious freedom in China, he and his wife have been boldly providing legal counsel for churches and persecuted rights defenders in Zhejiang.

"I urge the US government to work with the Chinese authorities for the immediate release of the Wen's family and other arrested innocent church leaders."

On April 14, a pastor's wife was killed in Henan province after stepping in front of a bulldozer to protest her church's demolition.