Four people found guilty of drug offenses were hanged today in the Iranian province of Kerman, ISNA reports, after the judiciary refused to commute their sentences.

They were charged with possession of between four to eight kilos of heroin or crack.

This is Iran’s second round of drug-related executions this week. On Tuesday, eight people were hanged in Orumiyeh and Miandoab in northwestern Iran for drug-related offenses.

The number of executions in Iran has surged dramatically in the past year, following the controversial presidential elections of 2009.

After China, Iran has the world’s highest annual execution rate, and human rights groups caution that these official statistics do not reflect the true number of executions.

Several human rights reports indicate that hundreds of prisoners were executed in Iran without official acknowledgement.