Amnesty International believes China carried out "thousands" of executions last year - the most in the world - however, the government keeps those records a state secret.
Amnesty International Senior Director Clare Algar said the continued fall in overall execution numbers was promising, however, she reiterated there was still a long way to go.
"A small number of countries defied the global trend away from the death penalty by increasingly resorting to executions," Ms Algar said.
"The death penalty is an abhorrent and inhuman punishment and there is no credible evidence that it deters crime more than prison terms."
There are 20 remaining countries responsible for all known executions around the world, with 106 countries having abolished the death penalty for all crimes.
Ms Algar called out both Saudi Arabia and Iraq for increasing their total number of executions.
"Saudi Arabia's growing use of the death penalty, including as a weapon against political dissidents, is an alarming development," she said.
"Also shocking was the massive jump in executions in Iraq, which nearly doubled in just one year."
China, Iran, Saudi Arabia, Iraq and Egypt were the five largest executing countries respectively last year, with the human rights group saying it believes Iran, North Korea and Vietnam are not disclosing the full extent of their executions.
Amnesty International acknowledged the US state of California for placing a moratorium on executions, as well as New Hampshire and Colorado for becoming the 21st and 22nd US states respectively to abolish the death penalty.
"Trends to abolish the death penalty in the United States demonstrate welcome human rights leadership in these turbulent times," Amnesty International senior program officer Kristina Roth said.
"Much more work still remains in our state legislatures, but the tide is moving in the right direction."
The US executed 22 people last year and handed down 35 death sentences - both figures which had decreased since 2018.
Texas remains responsible for more than 40 per cent of all the executions carried out in the US.