National police chief Khalid Abu Bakar said the new suspects are in addition to the seven North Koreans already being sought in last month's poisoning death of Kim Jong Nam at Kuala Lumpur's airport.
Khalid said the new suspects include an "important person," but he declined to give further details.
"I do not deny that there are more North Koreans involved in the murder of Kim Jong Nam. We will follow the legal channel to get them," he said. "I do not want to say more than that. If I do, they may run ... But we believe there is an important person too."
Four of the seven initial North Korean suspects left Malaysia on the same day of the killing. Police have obtained an Interpol red alert notice for the four men, believed to be back in Pyongyang.
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Police said the other three men are believed to be hiding in the North Korean Embassy in Kuala Lumpur.
Relations between Malaysia and North Korea have deteriorated sharply since Kim's death, with each expelling the other's ambassador.
Although Malaysia has never directly accused North Korea of being behind the attack, many speculate that it must have orchestrated it.
Experts say the VX nerve agent used to kill Kim was almost certainly produced in a sophisticated state weapons laboratory, and North Korea is widely believed to possess large quantities of chemical weapons.