One of the world's best known converts from Islam to Christianity has been diagnosed with advanced stomach cancer.

Nabeel Qureshi, a popular evangelist and travelling preacher whose new book No God But One: Allah or Jesus? was published yesterday, has cancelled nearly all speaking engagements while he "aggressively" persues healing, both "medical and miraculous", he wrote on his Facebook page.

"This is an announcement that I never expected to make, but God in His infinite and sovereign wisdom has chosen me for this refining, and I pray He will be glorified through my body and my spirit," he wrote.

Qureshi is married with a baby daughter.

"My family and I have received the news that I have advanced stomach cancer, and the clinical prognosis is quite grim. Nonetheless, we are going to pursue healing aggressively, both medical and miraculous, relying on God and the fact that He is able to do immeasurably more than all we ask or imagine," he says.

His spirits have "soared and sank" over the past few days as he pursues God's will and considers what the future holds, he continues.

"But never once have I doubted this: that Jesus is Lord, His blood has paid my ransom, and by His wounds I am healed"

He intends to blog or vlog his journey cancer and write about his struggle in a way that will glorify God.

He is also leaving Ravi Zacharias International Ministries, the Christian charity that he has served through being a travelling speaker for the past three years. A spokeswoman for the Oxford Centre for Christian Apologetics, where he is pursuing a doctorate in New Testament studies with the University of Oxford, said everyone there was "devastated".

Nancy Gifford, global media director of Ravi Zacharias, said: "The whole team is devastated by this diagnosis but we are committed to pray and fast for Nabeel. We love Nabeel, Michelle and Ayah and we trust that God will work for good even in these desparate circumstances."

Qureshi is still planning to write his next book, 20 Questions Muslims Ask and the Answers that Convert Them. 

And he has pleaded with friends and family "to fast and pray fervently" that he is healed.

"I do not profess to know the will of the Lord, but many of my close friends and confidants are convinced that this is a trial through which the Lord intends to bring me alive and refined."

Qureshi's first book, Seeking Allah, Finding Jesus, became a New York Times best seller. He believes the world is in the middle of an Islamic reformation. This means a return to the religion's fundamentals, and he believes these fundamentals are explicitly violent. He told Christian Today earlier this year: "There is a basis to believe in Jesus. He rose from the dead. You can check that historically. You don't have to believe it on blind faith. The Koran says if you believe Jesus is God, you will go to hell. (ch 5:72) whereas Romans (10:9) tells us we need to believe that to be saved. So they are exactly contrary. Therefore you cannot be both Christian and Muslim."

Ravi Zacharias himself told Christian Today: "When we shared a meal a few weeks ago, he had talked of terrible discomfort in his stomach. None had a sense of what lay ahead. Life brings its sudden turns. Our hearts go out to him and our prayers for him. No doubt this is a valley that no one anticipates so soon in life. The entire RZIM team and our families are in impassioned prayer on his behalf.

"Years ago when in Shanghai, the famed Chinese evangelist Wang Ming-Dao shared with me a song he sang every day when he was imprisoned for years, under the brutal Mao regime. I can just about hear him singing it now. The same comfort we seek in every crisis."