Kim Jong Nam, who has been living in exile with his family in Macau under Chinese protection, had spoken publicly in the past against his family's dynastic control of the isolated, nuclear-armed state.
South Korean and U.S. officials said he was assassinated by North Korean agents. North Korea has not acknowledged his death.
Malaysia's health minister Subramaniam Sathasivam said at a press conference on Sunday that autopsy findings were consistent with police reports showing Kim was killed by VX.
The minister said the chemical caused "serious paralysis which led to the death of the person in such a short period of time."
The Indonesian attacker, Siti Aishah, was reported to be unwell, possibly due to contact with the chemical.
Subramaniam said authorities were running tests to ascertain whether Siti was affected by the chemical.
Malaysia is considering shutting its embassy in Pyongyang or expelling North Korea's envoy as tensions escalate over the killing.
It said it may issue an arrest warrant for a North Korean diplomat wanted for questioning over the case but said "reasonable" time will be given for the diplomat to come forward before further action.
The diplomat is not known to have met the police yet.
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