The report added that AI "found only 701 individuals whose death sentences had been approved by the SPC between 2011 and 2016, while the organisation estimates that yearly the actual number runs into the thousands".
The report by Amnesty International also raises concerns that Britain may be "damping down" its criticism of countries that use the death penalty as it attempts to pursue post-Brexit trade deals and enters into new security arrangements.
"I think the most alarming thing is that China continues to give thousands of people death sentences per year and execute thousands and yet we don't know the extent".
The head of China's Supreme People's Court, Zhou Qiang, said in March the country has made sure to impose capital punishment on "an extremely small number of criminals who committed extremely serious crimes", according to the official Xinhua news agency.
Iran registered the second highest number of executions, more than 560, in 2016, and Vietnam may have put to death 429 people between August 2013 and June 2016.
The country then created military courts to try civilians suspected of terrorism-related offences. This is deliberately misleading, it said.
"China is a complete outlier in the world community when it comes to the death penalty, out of step with worldwide legal standards and in contravention with repeated United Nations requests to report how many people it executes".
In some cases, the report says, men were executed after confessing to crimes that had occurred months after they had been arrested.
In 2016, at least four of those executed in the country were convicted by the military courts. He had been executed 21 years earlier, at the age of 20.
Amnesty collects the data from official figures, media reports, and information passed on from people who have been sentenced to death, their families and their representatives.
Last year, Amnesty International revealed 1,634 executions took place in 2015 throughout the world in 25 countries.
"The magnitude of executions in Vietnam in recent years is truly shocking".
She says there is no evidence to support claims by authorities that the death penalty has any impact on the willingness of terrorists to carry out attacks. "You have to wonder how many more people have faced the death penalty without the world knowing it", said Salil Shetty. Nobody executes with such secrecy.
The US, for the first time since 2006, fell from its place in top five executors to seventh place behind Egypt.
The United States executed 20 past year, the lowest figure for the country since 1991.
But Amnesty cautioned that the drop in the USA can partly be attributed to legal challenges over the way lethal injections are carried out, and that when those cases are resolved there could be a jump in the number of people put to death.
"The debate is clearly shifting", he said in the group's annual global review of the death penalty, which showed a 37 percent decline overall.
In this Monday, April 10, 2017 photo, Amnesty International East Asia Director Nicholas Bequelin, left, and Deputy Director of Global Issues Programme James Lynch hold the copies of reports on the death penalty during a press conference in Hong Kong.
While opponents of the death penalty in the United States fight for its abolition, import regulations make its implementation increasingly hard for its advocates. But we have to fight to keep it that way.
Today 140 of the nations of the world have abolished capital punishment.