The trial of a group of human rights activists in Turkey took an unexpected turn on Wednesday night when a judge ruled they could be released from prison but must still face charges.

The campaigners, including several senior Amnesty figures, have been in prison since they were arrested during a human rights workshop in July and their prosecution has drawn criticism from Western governments.

Their trial on terrorism charges began on Wednesday but shortly before midnight the court handed down the surprise ruling that the defendants could be freed while the case continued.

The ruling was celebrated by the activists' supporters and seen by analysts as proof that international pressure had chastened Turkey's courts into releasing them.

"International condemnation clearly played a key role," said Howard Howard Eissenstat‏, an associate professor at St Lawrence University in New York. "Pressure can work, if it is applied with seriousness and coupled with consequences."