Rev Stuart Windsor (pictured above, right), a Special Ambassador for the organisation Christian Solidarity Worldwide (CSW), passed away at his home on Sunday morning.
CSW's Chief Executive, Mervyn Thomas said: "I have worked with Stuart for nearly a quarter of a century. I have known no-one with a more caring and compassionate heart for the suffering than Stuart."
Rev Windsor recently underwent angioplasty - heart surgery - after suffering a serious heart attack in July this year.
With deep sadness, we announce the death of our Special Ambassador, Rev Stuart Windsor. https://t.co/f51fv2Ay5W pic.twitter.com/pBYMfdp2Bb
— CSWPress (@CSWPress) September 18, 2017
He often put his own safety at risk to visit communities in countries where freedom of religion or belief is being undermined.
Speaking of his former colleague, Mr Thomas said: "He literally worked 24/7 for the cause of religious freedom, and no issue was ever too big or too small for him to take up."
During his life, Rev Windsor - who was in his 70s when he died - spoke at the United States Congress, the United Nations and European and UK parliaments.
He served for 19 years as National Director at Christian Solidarity Worldwide before entering retirement and becoming Special Ambassador.
Mr Thomas added: "Both the human rights and the Christian communities have today lost a giant of a man whose loss will be felt for a very long time to come.
"It has been an immense honour and a privilege to labour together with him for so long."
Click here to listen to Premier's Dave Rose speaking with CSW's Mervyn Thomas: