However Professor Todung Mulya Lubis, a prominent human rights lawyer in Indonesia, said he had asked Attorney-General H.M. Prasetyo to respect the legal process and not proceed with the executions until the outcome of the challenge was known.

He had requested to meet the Attorney-General but had been told he was too busy.

Profesor Mulya said constitutional court rulings were usually not retrospective and therefore would not directly affect Chan and Sukumaran's case.

"But we are talking about the life of people. If we ignore that it would be degrading the spirit of human rights."

Professor Mulya said the Attorney-General's spokesman, Tony Spontana, had told the media the executions would take place after the Asian-African conference, to be held in Indonesia from April 19 until April 24.

"Whether it's true or not only God knows because they keep saying over and over they will do the executions but they keep changing their position."

Professor Mulya said Chan and Sukumaran were the first people he had represented who were facing the death penalty.

He admitted to being shocked when President Joko Widodo rejected their clemency pleas in January without giving any reasons.

"Why am I pushing so hard [to fight their case]?" an impassioned Professor Mulya asked at a press conference on the constitutional court challenge.

"If I was in the shoes of Andrew Chan and Myuran Sukumaran I would want the right to know why my clemency had been rejected. This is not only for these two young men it's for others who deserve to know the grounds. This is for the constitutional process in Indonesia. We have to give reasons. We have to make it more humane. Clemency rejection is not about dehumanisation."

Chan and Sukumaran's legal team is asking the Constitutional Court to specify that the president must give reasons for clemency rejections under the clemency law.

The court action is being undertaken in conjunction with Indonesian human rights Organisations Kontras, Imparsial and Inisiator Muda.

Kontras spokesman Haris Azhar questioned why Indonesia was so eager to execute people.

He criticized the blanket rejection of the clemency pleas of drug felons,saying each of the 10 immediately facing the firing squad had individual cases that should be considered.

"We don't want to have the president making decisions as if he was committing genocide," Mr Haris said.

He also accused authorities of being secretive when it came to the death penalty.

Kontras was told by the Attorney General's office it could not have a list of those on death row because it was "classified" and death penalty cases could no longer be accessed on the Supreme Court website.

"I think people should be given the biggest opportunity to defend their lives. Unlike what we have today where information is not easy to get."

The press conference comes as Indonesian human rights group Migrant Care called on Indonesia to abolish capital punishment in the wake of the shock beheading of Indonesian maid Siti Zaenab in Saudi Arabia.

Zaenab, who had a suspected mental illness, was executed on Tuesday after she was found guilty of murdering her employer in 1999.

"The execution of Siti Zaenab Wahid, should provide momentum for the Indonesian Government to stop the practice of capital punishment in Indonesia," Migrant Care executive director Anis Hidayah said.

"The application of the death penalty at home will only make the Government lose its moral legitimacy to urge other countries to free Indonesian nationals who are on death row."

The Indonesian government issued a statement protesting against the Saudi Arabian authorities' failure to notify them or Siti Zainab's family before carrying out her execution.

Zaenab was sentenced to death in 2001. However after lobbying from former Indonesian president Abdurrahman Wahid, Saudi Arabia agreed to wait until her children were old enough to decide whether she should be pardoned.

The Indonesian government offered two billion rupiah (AU$200,000) in blood money and three Indonesian presidents - including Joko Widodo - made fruitless representations to save her life.

Migrant Care's Ms Anis said there were at least 290 Indonesian migrant workers facing execution in Malaysia, Saudi Arabia, Singapore, China and Qatar, 59 of whom had already been sentenced to death.

Meanwhile, Norwegian prime minister Erna Solberg asked Mr Joko to halt the executions when she met him for bilateral talks on Tuesday.

Norwegian academics worked with Sukumaran and Chan to introduce vocational courses at Bali's Kerobokan jail, including art classes.

They also held regular art auctions and exhibitions of the inmates' work to raise money for the rehabilitation program.