Pastor Duong Kim Khai, Tran Thi Thuy and Nguyen Thanh Tam are members of the unrecognised branch of the Mennonite church.

They were detained after helping people who had lost their farmland when it was forcibly sold by the local government to large corporations.

The Christians, all members of the Cow Shed Church in Ho Chi Minh City, were helping people to file complaint letters asking for compensation.

According to CSW, Pastor Duong Kim Khai was taken away from his workshop in Ho Chi Minh City on 10 August 2010 by a group of five or six people, who bundled him into a car with a Ben Tre registration plate.

His workshop was then searched and materials relating to complaint letters were confiscated.

Pastor Khai’s disabled wife and then 17-year-old son were not given arrest papers or details of Pastor Khai’s detention.

Those close to the case told CSW Pastor Khai is a gentle man who wanted to help others and speak up for injustice.

The three men have been held without access to lawyers or their families, reports Christian Solidarity Worldwide.

They are also said to be members of Viet Tan, an overseas-based democracy party.

They will be tried in Ben Tre province alongside four other activists facing the same charges with the same crime in Ben Tre province.

If convicted, they face a lengthy prison sentence or even a death sentence.

CSW said the charges, defined under Article 79 of the Criminal Law, were "ill-defined".

The organisation said human rights activists were under "huge pressure" in Vietnam and that there had been an increase in arrests and restrictions on freedom of expression in recent months.

CSW’s Advocacy Director Andrew Johnston said: “CSW calls upon the Vietnamese authorities to allow Pastor Duong Kim Khai, Tran Thi Thuy and Nguyen Thanh Tam access to legal representation at the trial, and for it to follow due procedure as defined in international law.

"They are facing lengthy sentences for peacefully standing up for the rights of fellow citizens.

"CSW requests that these men, whose cases are representative of the pressures facing human rights defenders, be released immediately to their families.”