KHARTOUM (Reuters) - Sudan sentenced six children to death for taking part in a Darfur rebel attack on Khartoum but has since promised not to execute them, a top United Nations official said on Sunday.

A Sudanese government official said he could not comment on the case but added child executions were not allowed under the law and there were checks to keep youngsters off death row.

"We have six from the attack on death row," said Radhika Coomaraswamy, the U.N. Secretary-General's special representative for children and armed conflict.

"The government claims that a military panel has found that these were not children. But the assessment of the international agencies is that they are children."

"I was assured today by the minister of justice that they will not be executed," she told reporters at the end of a trip to Sudan.

The United Nations defines a child as anyone under 18.

More than 100 people were sentenced to death after being convicted of taking part in an attack by Darfur's rebel Justice and Equality Movement (JEM) on the Khartoum suburb of Omdurman in May last year.

Sudan's president Omar Hassan Al-Bashir pardoned and freed scores of children he said had been detained after taking part in the unprecedented raid, which stopped just short of the country's parliament.

Coomaraswamy said U.N. staff had identified another six children among the remaining convicts, but Sudan's government had said some of them were over 18 at the time of the attack.