A statement purporting to come from a son of Osama bin Laden denounced the al-Qaida leader's killing as "criminal" and said his burial at sea had humiliated the family, Reuters reports, citing an online monitoring service.

The statement, attributed to Omar bin Laden, bin Laden's fourth eldest son, said the al-Qaida chief's children reserved the right to take legal action in the US and internationally to "determine the true fate of our vanished father," the SITE Intelligence Group said.

There was no independent confirmation of the authenticity of the letter, although several specialists on militant propaganda said the text appeared genuine.