CILACAP, Indonesia (AFP) - The mother of an Australian drug trafficker on death row in Indonesia said Tuesday he would be executed by firing squad at midnight (1700 GMT).

"I won't see him again. They are going to take him at midnight and shoot him," Raji Sukumaran, the mother of Myuran Sukumaran, tearfully told reporters.

Sukumaran is one of eight foreigners due to be put to death imminently in Indonesia. Nationals from Brazil, the Philippines and Nigeria are also among the group.

Preparations are under way for the executions on the prison island of Nusakambangan, where Jakarta puts condemned prisoners to death, but authorities have refused to disclose when the executions will take place.

"I am asking the government not to kill him. Please, president, don't kill him today," she said, appealing to Indonesian President Joko Widodo, who has been a vocal supporter of using the death penalty against drug traffickers.

"Call off the execution. Please don't take my son."