Iran last year maintained its grim record of executing more people per capita than any other country in the world, the majority for drug-related offenses, according to the latest report by Ahmed Shaheed, the UN Special Rapporteur on the situation of human rights in Iran.

The report, which was shared with Al-Monitor in advance, states that Iranian authorities executed between 966 and 1,054 people in 2015, including four people under the age of 18. The total reflects a tenfold rise over the past decade and exceeds the 2014 figure by more than 200.

Saudi Arabia, which has a much smaller population than Iran, executed 151 people last year and appears to be on track to execute more this year. China, the world's most populous nation, is believed to have executed the largest number of individuals last year — estimates are well above 1,000 — but per capita, Iran exceeds all other countries.

Stung by international and domestic criticism over this grim statistic, Iran has begun to debate substituting life in prison for the death sentence for many drug offenses, which accounted for 65% of those executed last year, according to the UN report.