Malaysian Deputy Prime Minister Ahmad Zahid Hamidi yesterday was quoted by national news agency Bernama as saying that Kang's expulsion was a "clear message to the North Korean government that we are serious about solving this problem and we do not want [the investigation] to be manipulated".
Last Saturday, Malaysia's foreign ministry declared Mr Kang a persona non grata, and told the North Korean Embassy that Mr Kang must leave Malaysia by 6 pm today.
Diplomatic ties between Malaysia and North Korea have soured since the murder, which South Korea and the United States allege was an assassination organised by North Korean agents.
US and South Korean officials had claimed Kim Jong Nam was killed by agent's of the North Korean regime. However, he said a series of executions carried out by Kim Jong Un could indicate his power might be insecure.
Jong-nam was at the KL International Airport 2 (klia2) on Feb 13 to board a flight to Macau when two women suddenly appeared before him and allegedly wiped his face with their hands laced with what was later identified as the VX nerve agent.
Ri Jong Chol, who had been detained since February 17, was handed over to immigration officials for deportation.
Kang also accused Malaysia of police brutality against a North Korean chemist suspected in Kim's death, claiming cops pointed guns at his family members and beat his teenage son in the face.
Huong together with an Indonesian woman were captured in surveillance video at the Kuala Lumpur airport where Kim Yong Nam was fatally poisoned on February 13.
Kang had strained ties between both counties after he criticised Malaysia for refusing to release the body of Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un.
The announcement came after the ambassador, who was summoned to the Foreign Affairs Ministry at 6pm on Saturday, failed to turn up. The autopsy is especially sensitive because North Korea had asked Malaysia not to perform one, but authorities said they had to under the law.
Shahriman Lockman, a senior analyst at the Institute of Strategic and International Studies Malaysia, said it is possible that they were all hiding in the North Korean embassy - making them virtually untouchable.
Ri was detained four days after the attack but police never said what they believed his role was.
North Korea also asserted that the man died of a heart attack and not of poisoning from the highly toxic VX nerve agent.
Once deemed heir apparent to his late father, Kim Jong Il, who ruled the country from 1994 to 2011, Kim Jong Nam lived in a de facto exile after falling out of favor with him. "North Korea can say what they like but the facts remain", Khalid told the AP.
North Korea has strongly rejected the allegations.
For North Korea, agent VX may have been the ideal weapon for assassination.