The number of known executions worldwide rose to at least 778 last year following a surge in Iraq and Iran, Amnesty International said today, but China remains the world's biggest state executioner by far.
Beijing is thought to have killed thousands of its own citizens, more than the rest of the world put together, the London-based human rights organisation said.
But the charity's annual report on death sentences and executions worldwide said the Chinese authorities "continue to treat the figures on death sentences and executions as a state secret".
"We need really to spotlight China's secrecy around the death penalty," Audrey Gaughran, Amnesty's director of global issues told AFP.
"The authorities in China said that since 2007 they have reduced the use of the death penalty. So our challenge to them is if you have, publish the data and show us," she said.
Although Beijing said in November it would reduce the number of crimes eligible for the death penalty from the current 55, it still led the top five countries using the death penalty in 2013, followed by Iran, Iraq, Saudi Arabia and the United States.
The rise in the known judicial uses of the death penalty - from at least 682 in 2012 - was chiefly due to Iraq and Iran, the report said.
Iran put at least 369 people to death in 2013, up from at least 314 in 2012, and Amnesty said there was credible evidence from sources in the country that at least 335 further executions were carried out in secret.
Iraq executed at least 169 people in 2013, a sharp rise on the 40 given the death penalty in 2011 and 101 put to death in 2010, with death sentences there often passed after "grossly unfair trials", the report said.
"The virtual killing sprees we saw in countries like Iran and Iraq were shameful," said Amnesty secretary general Salil Shetty.
"But those states who cling to the death penalty are on the wrong side of history and are, in fact, growing more and more isolated.
"Only a small number of countries carried out the vast majority of these senseless state-sponsored killings. They can't undo the overall progress already made towards abolition."
People were executed in 22 countries in 2013, one more than the previous year, although Indonesia, Kuwait, Nigeria and Vietnam all resumed use of the death penalty.
