Amnesty International's report on capital punishment reiterates that while China hides the scale of executions, an investigation shows the country executes more people than any other in the world.
The number of state executions and countries imposing and carrying out death penalties decreased in 2016, Amnesty International revealed on Tuesday.
The UK-headquartered human rights organisation said China is believed to have executed "thousands" of people, more than the global figure of at least 1,023 executions in 23 other countries in 2016.
China, where public execution data is a state secret, executed more people in 2016 than all other nations combined, another Amnesty investigation revealed.
Despite local media reports saying at least 931 individuals were executed between 2014 and 2016, only 85 of them were in the online database, Amnesty said.
"Nobody executes at that scale. Nobody executes with such secrecy. Nobody executes so quickly," said Amnesty International's regional director for East Asia, Nicholas Bequelin.
China's Supreme People's Court head Zhou Qiang, said in March China made sure to impose capital punishment on "an extremely small number of criminals who committed extremely serious crimes," according to Xinhua news agency.
But Bequelin called Zhou's statement "misleading and disingenuous."
Vietnam executions revealed
In Malaysia and Vietnam, new disclosures revealed the executions in those countries are higher than previously thought.
"The magnitude of executions in Vietnam in recent years is truly shocking," Amnesty's Secretary General Salil Shetty said.
Vietnam has secretly been one of the world's biggest executioners over the last three years, executing 429 people between August 6, 2013 and June 30, 2016. Only China and Iran executed more people during that period. Amnesty did not manage to find any data on 2016 figures.
The report also revealed that more than 1,000 people are on death row in Malaysia while nine people were executed in 2016.
US drops from world's top five
The US is no longer among the world's top five executioners for the first time since 2006. It executed 20 people last year, which is the lowest annual figure for the country since 1991.
The number of executions has been falling since 2009, while the number of death sentences was the lowest since 1973.