Human rights group Amnesty International says the total number of known worldwide executions has reached its highest level since 1989.
On Wednesday, the London-based rights group said in its annual report that the number of executions rose by more than half last year, reaching 1,634.
The figure shows a 54-percent rise from the 1,061 executions recorded in 2014.
"The rise in executions last year is profoundly disturbing," Amnesty’s secretary general, Salil Shetty, said, adding, "Not for the last 25 years have so many people been put to death by states around the world.”
The watchdog added that the number does not include those in China, which treats the death penalty as “a state secret,” similar to Vietnam and Belarus. Beijing is believed to have executed thousands of its citizens during this time period.
According to the report, 25 countries around the world carried out executions by beheading, hanging, lethal injection, or shooting in 2015 for crimes such as murder, drug-related offences, corruption, armed robbery, adultery, aggravated rape, rape, and kidnapping.
The report on executions in 2015 comes after Pakistan lifted a six-year moratorium on the death penalty following a school massacre by Taliban militants in December 2014, which left some 150 people, including many students, dead.
Earlier this year, Amnesty voiced concern over Saudi Arabia’s controversial execution of prominent Shia cleric, Sheikh Nimr al-Nimr, along with 46 others, including activists.
Amnesty’s Middle East and North Africa director Philip Luther said Riyadh, which carried out more than 150 death sentences in 2015, had carried out executions to clamp down on dissent.