Sydney: A Brazilian man executed in Indonesia for drug trafficking who was diagnosed with schizophrenia and bipolar disorder did not understand what was happening to him until his final moments, a priest assigned as his spiritual adviser told Australia's ABC radio on Thursday.

Rodrigo Muxfeldt Gularte was among eight people convicted of drug offences from several countries who were executed shortly after midnight on Wednesday morning.

Brazil had made repeated personal pleas for Indonesia to commute his sentence on humanitarian grounds, citing his mental illness.

Father Charlie Burrows, a local priest who accompanied Gularte in his final hours, told ABC he thought he had prepared the Brazilian for the execution.

‘I thought I'd got him ready, that he was going to be put in chains, because he didn't like being touched ... I said to him, well I'm 72, when you get up to heaven you'll know where I'm going to live, prepare a garden or something,’ Burrows said.

Gularte was calm as he was handcuffed by warders but became agitated when he was handed over to police outside the jail who put leg chains on him, Burrows said.

‘I thought he'd got the message he was to be executed but ... when the chains started to go on, he said to me, 'Oh father, am I being executed?',’ Burrows said.

Burrows, who witnessed the execution of another Brazilian prisoner in January, said Gularte continued to hear voices in his final days telling him everything would be fine.

‘He believes the voices more than he does anybody else,’ he said.

Gularte was caught entering Indonesia in 2004 with six kilograms of cocaine hidden in surf boards, and was sentenced to death in 2005.

The 42-year-old's family presented several doctors' reports to the Indonesian authorities attesting to his mental illness, and Brazilian President Dilma Rousseff had made personal pleas on his behalf. Rousseff recalled Brazil's ambassador to Jakarta after the first execution in January.

Burrows joined other spiritual advisers and family members in a tent near the field on the prison island of Nusakambangan where the executions took place. They heard the men singing before shots rang out simultaneously and were comforted that there were no subsequent single shots that would have indicated one of the prisoners needed to be shot in the head.

Burrows said all eight men refused blindfolds and were handcuffed at the front to allow them to shake hands with a large number of warders who had gathered outside.

‘They might have seen the executioners in very dark colours; it was a very dark night,’ Burrows said. ‘They only had flashlights on the prisoners, and when we were going to meet them we were falling over stones because of the dark.’