Osama Bin Laden's son has denounced the Al Qaeda leader's killing as 'criminal' and said he reserves the right to take legal action against America.

The statement apparently made by Omar Bin Laden has appeared on an Islamist website.

Omar, who is Bin Laden's fourth eldest son, claimed he and the Al Qaeda chief's other children are reserving the right to take legal action in the U.S. and internationally to 'determine the true fate of our vanished father', said the SITE Intelligence Group, an online monitoring service.

He also branded his father's burial at sea as a 'humiliation' for his family.

There was no independent confirmation of the authenticity of the letter.  

Several specialists on militant propaganda said the text appeared genuine.

The news came as it emerged the CIA will allow a select few lawmakers to view the controversial pictures of Osama Bin Laden's corpse.

The CIA will allow the group to see the photos only if they travel to the agency's headquarters.

The move came as the White House faced renewed pressure to release the grisly images, following a series of requests filed under the Freedom of Information Act.

News organisations, public interest groups and even one politician have all lodged official demands with government agencies to see the photographs of Bin Laden's body after he was shot dead last week at the Abbottabad compound in Pakistan.

President Obama has so far strongly resisted calls to release the pictures as 'proof' of the terror chief's death at the hands of U.S. special forces.