The sons of Osama Bin Laden have criticised the US authorities for carrying out his "arbitrary killing".A statement given to the New York Times newspaper said the family wanted to know why the al-Qaeda leader had not been captured alive.
Omar Bin Laden has repeatedly distanced himself from his father in the past
Relatives who survived the 2 May raid in Pakistan should be freed, it said.
Another statement appeared on a jihadist website saying the burial of Bin Laden at sea "demeans and humiliates his family".
Osama Bin Laden was shot dead by US special forces during a raid on his home in the Pakistani town of Abbottabad.
US officials have said that while Bin Laden was unarmed he had given no indication to the US troops that he wanted to surrender.
Attorney General Eric Holder has said that the killing was lawful and "an act of national self-defence".
The statement printed by the New York Times was attributed to Bin Laden's fourth son, Omar Bin Laden, who has repeatedly distanced himself from his father's ideology.
It said that in absence of a body or photographic evidence, the family were not convinced he was dead.
But if he was dead, it said, they were questioning "why an unarmed man was not arrested and tried in a court of law so that truth is revealed to the people of the world".
They argue Bin Laden's killing had broken international law and that figures such as former Iraqi President Saddam Hussein and Serbian President Slobodan Milosevic had been given the chance to stand trial.
"We maintain that arbitrary killing is not a solution to political problems and crime's adjudication as justice must be seen to be done."
The family said they were demanding a enquiry into why Bin Laden was "summarily executed without a court of law" and demanded the release of his three wives and several children, who are believed to be in Pakistani custody.
The statement also said the US decision to bury Bin Laden's corpse at sea had deprived the family of performing religious rites.
A slightly different version of the report was published on a jihadist websites, said the SITE Intelligence Group.
It said US President Barack Obama was "legally responsible" for clarifying "the fate of our father" and that the sea burial "demeans and humiliates his family and his supporters".
US President Barack Obama has urged Pakistan to investigate how the al-Qaeda leader could live in the garrison city of Abbottabad undetected and to find out if any officials knew of his whereabouts.
Pakistan's PM Yousuf Raza Gilani has insisted that allegations of Pakistani complicity and incompetence are "absurd".