A rising number of executions in Iran helped push the known world total to at least 676 in 2011, Amnesty International said on Tuesday, while stressing the global figure was far below reality.
China is still executing thousands of people every year, more than the rest of the world put together, Amnesty said in its annual review of death sentences and executions worldwide.
But the number of countries using the ultimate penalty continued to fall and even China reduced the number of offences attracting it, the London-based rights group said, expressing some optimism.
Amnesty singled out "a significant increase in judicial killings in Iran, Iraq and Saudi Arabia."
Iran executed at least 360 people -- three-quarters of them for drugs offences -- Saudi Arabia at least 82, Iraq at least 68 and Yemen at least 41, the report said.
The rise in Iran (up from at least 252) and Saudi Arabia (up from at least 27) alone more than accounted for the 149 net increase in known executions across the world, compared to 2010.
Amnesty said it had credible reports of at least a further 274 unconfirmed or even "secret" executions in Iran.
At least three people killed by Tehran were under 18 when they committed their crimes. There are reports of four further juvenile offender executions in Iran, and one in Saudi Arabia.
The Arab uprisings changed the political landscape in North Africa and the Middle East in 2011 but hopes that this would lead to changes to the death penalty "have yet to be realised", Amnesty said.
Though the total number of death sentences in the region decreased by a third compared to 2010, executions increased by almost half, due to Iran, Iraq and Saudi Arabia.
Amnesty secretary general Salil Shetty said, however, "Even among the small group of countries that executed in 2011, we can see gradual progress. These are small steps but such incremental measures have been shown ultimately to lead to the end of the death penalty.
"It is not going to happen overnight but we are determined that we will see the day when the death penalty is consigned to history."
People were executed or sentenced to death for offences including adultery, sodomy, apostasy and "enmity against God" in Iran, blasphemy in Pakistan, sorcery in Saudi Arabia and the trafficking of human bones in the Republic of Congo, said Amnesty.
Some 18,750 people were under a death sentence at the end of 2011, compared to 17,833 in 2010.
But only 20 countries used capital punishment last year, down from 23 in 2010, and 31 a decade ago.
"The vast majority of countries have moved away from using the death penalty," Shetty said.
"Our message to the leaders of the isolated minority of countries that continue to execute is clear: you are out of step with the rest of the world on this issue and it is time you took steps to end this most cruel, inhuman and degrading punishment."
Amnesty said 96 countries had so far abolished the death penalty. Nine have abolished it for ordinary crimes, 35 can be considered abolitionist in practice, having conducted no executions in the last 10 years, and 58 have retained it for ordinary crimes.
China has abolished the death penalty for 13 mainly "white collar" crimes, Amnesty said, but it still executed more than the rest of the world put together. Amnesty urged Beijing to publish data on those killed or sentenced to death.
Public executions were carried out in Iran, Saudi Arabia, North Korea and Somalia.
Amnesty said China, Iran, Iraq, North Korea and Saudi Arabia were using "confessions" obtained through torture.
The methods used for execution in 2011 were beheading, hanging, lethal injection and shooting.