Nearly 4,000 people were executed worldwide in 2004 - the most in nearly a decade, Amnesty International says.
In Iran, the death penalty sometimes comes after a flogging
China carried out more executions than all other countries combined - at least 3,400 - the human rights group says.
The global rise in executions was "alarming", said Amnesty's UK director Kate Allen, who called the figures from China "genuinely frightening".
China says it will tighten conditions under which people can be executed, and the US has already done so.
The US came fourth in Amnesty's table of executions, with 59 in 2004.
Iran came second, with at least 159, followed by Vietnam with at least 64.
The 3,797 executions in 2004 were the second-largest annual total in the last 25 years, the organisation said.
And it noted that its numbers represented the minimum number of executions it could confirm.
"Many countries continue to execute people in secret," Ms Allen said.
China's Premier Wen Jiabao said last month that Beijing would improve its justice system so the death penalty would be given "carefully and fairly", the official Xinhua news agency reported.
Sarah Green, a spokeswoman for Amnesty in London, welcomed the announcement, but said the group wanted action, not words.
"It is good to hear people talking about changing their systems. We look forward to seeing the results," she told the BBC News website.
The organisation has two objections to the death penalty, she said - it violates fundamental rights and is applied unfairly.
"There is lots of evidence to show this is not a perfect punishment," she says.
It was more likely to be applied to "people who cannot afford lawyers, who cannot get anyone to stand as a witness for them," she added.
"Discrimination soon enters the equation, for women in particular. It's very concerning."
The United States - one of the very few democracies on Amnesty's list - last month banned the death penalty for crimes committed by minors.
The number of death sentences is falling in the US, according to the New York Times.
Many US executions are carried out by lethal injection
A total of 144 death sentences were handed down in 2003, the lowest level since 1977, the newspaper reported.
Ms Green welcomed the fall in death sentences, but said the US should go further and ban the death penalty.
"We believe it's wrong. The cardinal basic human rights laws say there is a right to life and a right not to be punished in a cruel way."
She disputed surveys that show a majority of Americans support the death penalty.
Slightly more Americans opposed the death penalty than supported it - if a life sentence without the possibility of parole was the alternative, she said.
More than 100 people had left death row in the US when their convictions were overturned, she said.
"There is so much evidence that the death penalty is being applied unfairly, the very possibility of executing anybody who is innocent is reason not to have it," she said.
And she cited a question former UK Prime Minister Ted Heath asked of death penalty supporters: "The real test is, is that person willing to be the innocent one who is executed?"