Tim Keller's family is asking for prayers after the popular pastor and author, who is battling cancer, was readmitted to hospital. 

His son, Michael Keller, said on Twitter that his father had to return to hospital on Sunday, just one day after he had been released.

At the weekend, his wife, Kathy Keller, shared that the pastor had experienced "complications" from his treatment for pancreatic cancer but had been allowed to go home to continue his recovery.

Michael Keller's tweet on Wednesday confirmed that he has had to go back to the hospital.

The tweet asked for prayer. 

"A brief health update on my Dad: After being released from the hospital on Saturday, he returned late Sunday night to receive additional care. Please continue to pray for his recovery," he wrote.

Tim Keller has been fighting stage four pancreatic cancer for the last three years and has endured gruelling treatment, including immunotherapy last year.

Despite the success of that treatment, he updated supporters in March with the news that some new tumors have grown, meaning that he needed more immunotherapy. 

It is this treatment that has caused the "complications" detailed by his wife. She wrote on Saturday, "Please continue to pray during this slow recovery."