TEMPO.CO, Jakarta - The U.N. human rights chief on Wednesday urged the Indonesian government to abandon plans to execute more than a dozen people for drug offenses.

High Commissioner for Human Rights Zeid Ra'ad Al Hussein said the U.N. Human Rights Office is "deeply concerned" by death penalty cases that lack transparency and compliance with the right to receive a fair trial, including the right to an appeal.

He called on the government of President Joko "Jokowi" Widodo to impose an immediate moratorium on executions.

Security has been tightened at Nusa Kambangan prison island in preparation for the executions of the mostly foreign drug convicts by firing squad.

It would be the third set of executions under Jokowi, who campaigned on promises to improve human rights in Indonesia. His 2-year-old administration will have executed more people than were executed in the previous decade if the government sticks to its plans.

"The increasing use of the death penalty in Indonesia is terribly worrying and I urge the government to end this practice, which is unjust and incompatible with human rights," Zeid said in a statement.

He said the death penalty is not an effective deterrent.

Muhammad Rum, a spokesman for Indonesia's attorney-general, said the executions are the "implementation of our positive laws" and will not be delayed or stopped. All the cases have gone through a long legal process including appeals, he said. "They all have been given chances at all stages."

Lawyers and rights groups have raised serious doubts about the legitimacy of the convictions in several of the death row drug cases.

Last year, Indonesia executed 14 people convicted of drug crimes, mostly foreigners, sparking an international outcry.

Jokowi's predecessor ended a moratorium on executions in 2013.

AP