Iran has gone on an execution binge in the past two weeks, hanging some 40 people, including 19 in one day, according to international human rights groups inside and outside of Iran.

Iran hanged a total of 19 prisoners on Tuesday, including one who was executed publicly, according to the Iran Human Rights Documentation Center (IHRDC), which tracks the Islamic Republic’s flawed judicial system.

Forty executions have taken place since the beginning of January, including 33 in just the past week, according to human rights group Amnesty International.

Iran, which human rights activists say is one of the world's leaders in the abuse of prisoners, hit an all time execution peak in 2013 when it killed some 529 citizens.

The rate of executions has spiked under the leadership of President Hassan Rouhani despite his claims to be a "moderate" reformer.

More than 300 people were killed in the months after Rouhani assumed office, prompting criticism from human rights activists who criticized him for not living up to his moderate claims.

"The spike in the number of executions carried out so far this month in Iran is alarming," Hassiba Hadj Sahraoui, Amnesty International’s deputy director for the Middle East and North Africa said on Thursday in a statement. "The Iranian authorities’ attempts to change their international image are meaningless if at the same time executions continue to increase."

Iran has a penchant for hanging criminals publicly from a crane, where observers can gather to watch the execution.

Iran has officially admitted to killing 21 people since the start of 2014, according to Amnesty, which recorded an additional 19 executions that were not officially reported.

Iran has killed more people since last Thursday than it did in the entirety of January 2013.

Observers say Iranian courts are notoriously flawed and marred by corruption, noting that those convicted of even minor drug offenses are frequently killed.

"In Iran, drug-related offences are tried in Revolutionary Courts which routinely fall far short of international fair trial standards," said Amnesty’s Sahraoui. "The reality in Iran is that people are being ruthlessly sentenced to death after unfair trials, and this is unacceptable."

Eleven of the 19 executions on Tuesday secretly took place inside Iran’s Rajai Shahr prison of Karaj, located just outside of Tehran, Iran Human Rights reported. Those killed were accused of murder.

Another seven, the majority of them charged with drug offenses, were hanged in various locations across the country.

One man was hanged publicly in the town of Saveh, also located outside of Tehran.

"He was sentenced to ‘twice retribution’ in public, and his death sentence was carried out publicly," according to Iran Human Rights, which published a picture of the man dangling from a crane.

The execution of drug offenders does not comport with international standards, according to Amnesty, which urged Iran to stop killing people en masse.