JAKARTA: Indonesia has begun talks with Britain to repatriate the most prolific rapist in British history, a senior minister said, following its move to also seek the return of a Guantanamo Bay detainee accused of being one of the Bali bomb plotters.

Reynhard Sinaga, 41, was found guilty in Manchester in 2020 of assaulting 48 men whom he drugged after taking them back to his apartment from bars and clubs in the British city.

A Manchester court ruled that Sinaga must serve at least 30 years in prison for a total of 159 offences committed from January 2015 to May 2017.

Indonesia's senior minister for law and human rights affairs Yusril Ihza Mahendra told reporters late on Thursday that talks with the British government were at an early stage.

The mechanism for such a repatriation would be decided later, he said, either through a prisoner transfer or through an exchange with a British prisoner jailed in Indonesia.

"No matter how wrong a citizen is, the country has the obligation to defend its citizen," Yusril said.

"It's not an easy job for us," he said, adding there are many things that need to be negotiated with the British government.

The British embassy in Indonesia did not immediately respond to a request for comment.

Indonesia is also looking at ways to repatriate Riduan Isamuddin, better known as Hambali, who was accused of being involved in some deadly attacks including the 2002 Bali bombings.

Under British rules, Sinaga is only able to file for leniency after he has been in jail for 30 years, Yusril said.

Sinaga's family have met with the ministry's representative to seek his repatriation.

If the British government agrees to his return he would be jailed in a maximum security prison, Yusril said. "Otherwise he will cause new problems."

Sinaga, who has been in the UK since 2007, targeted young men who looked drunk or vulnerable and rendered them unconscious with a sedative.

The rape investigation was the largest in British legal history.