Sirul Azhar Umar must reveal what he knows before an investigation can be launched, said former inspector-general of police Musa Hassan.

“The police cannot investigate if he just threatens to do so. It is like he wants to say but doesn’t say,” he told Malaysiakini.

However, Musa said Sirul should disclose under whose orders he acted and the people whom he claims had a motive to kill Altantuya Shaariibuu but are still free.