GENEVA (Reuters) - At least 1,526 people were executed worldwide last year, with 80 percent of all known executions carried out in China, Iran and the United States, Amnesty International said on Friday.

The London-based human rights group also expressed concern that U.S. military tribunals which will prosecute "terrorist" suspects will have the power to impose death sentences which cannot be appealed.

In a report issued in Geneva, where the United Nations Commission on Human Rights is holding its annual six-week session, Amnesty urged the 53-member body to speak out against the supreme punishment and build pressure for a global moratorium on executions.

Some 111 countries have abolished the death penalty in law or in practice but it is still imposed in 83 countries, it said.

"The death penalty is the most absolute form of a human rights violation," Amnesty's Andrea Huber told a news briefing.

"The top three executioner states were China -- with 1,060 executions in only one year -- Iran with 113 executions and the United States with 71 executions," she added.

While the number of executions worldwide appeared to have halved in 2002 from 3,048 executions in 2001, it was difficult to compare as the true number of people executed in China was believed to be much higher, according to Amnesty.

In addition, at least 3,248 people were sentenced to death in 67 countries in 2002, it said.

"For many, Amina Lawal became a symbol of the horrifying truth of the death penalty. She was sentenced to death by stoning in Nigeria for having a baby out of wedlock," Huber said. "Her appeal is still pending."

U.S. DENOUNCED

Amnesty denounced the United States for executing three death row prisoners last year who were convicted for crimes committed when they were under age 18.

"It is a practice that violates international law...There are many, many juvenile offenders on death row," Huber said.

In total, 3,700 prisoners were under sentence of death in the United States as of January 2003, according to the report.

Huber added: "We know that there are many innocent people who are sentenced to death."

More than 100 death row inmates who proved their innocence have been released in the 30 years since U.S. Supreme Court rulings led to resumption of executions, according to Amnesty.

Number 100 was Ray Krone, a former death row prisoner in Arizona, released almost exactly a year ago after DNA testing proved his innocence. He had been convicted by two juries for the murder of a barmaid at a bar where he played darts.

"I am one of the few fortunate ones who had a chance to prove their innocence. It took a lot of work, perseverance and money," he told reporters.

Krone, who spent more than 10 years in prison, including 32 months on death row, had previously served in the U.S. air force.

"I am not proud of our justice system. Nobody who has seen what I have seen or experienced what I have could ever support the death penalty," he said.

"I was naive, ignorant of how the system really worked. I believed that innocence was protection, that truth meant justice would be forthcoming," Krone said. "I am going to do everything that I can to expose the death penalty for what it really is -- a tool used by prosecutors and police to gain career advancement and to put politicians in office."