Trafficking investigations into hundreds of Pakistani women and girls being sold as brides to Chinese men have reportedly ground to a halt because of government reluctance to harm ties with Beijing.

Pakistan's government has pressured investigators and witnesses to halt cases which could have damaged relations with China, as its ally pours huge amounts of investment into the country.

Investigators have compiled a list of 629 girls and women who were sold as brides to Chinese men and taken to China, according to an investigation by The Associated Press.

The biggest case against traffickers has fallen apart, with a court in Faisalabad acquitting 31 Chinese nationals charged in connection with trafficking. Women who had initially been interviewed by police refused to testify after being threatened or bribed into silence, according to a court official and a police investigator familiar with the case.

Saleem Iqbal, a Christian activist who has helped parents rescue several young girls from China, told AP that the government had also put “immense pressure” on investigators.

“Some [Federal Investigation Agency officials] were even transferred,” Mr Iqbal said.