Indonesia has in recent weeks released half a dozen high-profile detainees, including a Filipina mom on death row and the last five members of the so-called "Bali Nine" drug ring.

French diplomats have acknowledged that talks were underway for the transfer of Serge Atlaoui, a 61-year-old Frenchman arrested in 2005 at a secret drugs factory outside capital Jakarta.

Jakarta has now confirmed it received the official transfer request.

"We have received a formal letter requesting the transfer of Serge Atlaoui," Coordinating Law, Human Rights, Immigration and Correctional Services Minister Yusril Ihza Mahendra told AFP.

He said it would be studied and discussed in early January after the holidays.

The French embassy in Jakarta declined AFP's request for comment. 

Father-of-four Atlaoui has maintained his innocence, claiming that he was installing machinery in what he thought was an acrylics plant.

He was initially sentenced to life in prison, but the Supreme Court in 2007 increased the sentence to death on appeal.

Atlaoui was held at the Nusakambangan prison island in Cilacap, Central Java following the death sentence, but he was transferred to Tangerang penitentiary in Banten in 2015 ahead of his appeal.

That year, he was due to be executed alongside eight other drug offenders but won a temporary reprieve after Paris stepped up pressure, with Indonesian authorities agreeing to let an outstanding appeal run its course.

In the appeal, Atlaoui's lawyers argued that then-president Joko "Jokowi" Widodo did not properly consider his case as he rejected Atlaoui's plea for clemency, typically a death row convict's last chance to avoid the firing squad.

The court, however, upheld its previous decision that it did not have the jurisdiction to hear a challenge over the clemency plea.

Atlaoui's lawyer, Richard Sedillot, told AFP last month that there was still "considerable hope" for a transfer.

Earlier this month, Filipina inmate Mary Jane Veloso tearfully reunited with her family after nearly 15 years on Indonesia's death row. She was transferred to a women's prison in Manila where she awaits a hoped-for pardon for her drugs conviction.

Indonesia has some of the world's toughest drug laws and has executed foreigners in the past.

At least 530 people were on death row in the Southeast Asian nation, mostly for drug-related crimes, according to data from rights group KontraS, citing official figures. According to Indonesia's Immigration and Corrections Ministry, more than 90 foreigners were on death row, all on drug charges, as of early November.

Despite ongoing negotiations for prisoner transfers, the Indonesian government recently signaled that it will resume executions, on hiatus since 2016, of drug convicts on death row.