Kim Chol is the alias used by Kim Jong-nam, who is the half-brother of North Korean leader Kim Jong-un, whenever he travelled.
Indonesians Raisa Rinda Salma, 24, and Dessy Meyrisinta, 33, together with locals Tham Yook Kun, 50, and Ng Wah Hoong, 38, are being sought by the authorities.
"Efforts to trace all four witnesses have been fruitless until now.
"Checks on their movement via the Immigration Department show that all are still in the country," said Selangor CID chief Senior Asst Comm Fadzil Ahmat in a statement on Tuesday (Jan 8).
"The aforementioned witnesses are urged to present themselves at the Serdang police headquarters, or contact investigating officer ASP Wan Azirul Nizam Che Wan at 019-4811844," he added.
Siti Aisyah from Indonesia and Doan Thi Huong from Vietnam have been on trial for over a year, accused of murdering Jong-nam by smearing nerve agent VX on his face at Kuala Lumpur airport.
The brazen assassination in February 2017 shocked the world but the women have denied murder, saying they believed they were taking part in a prank and were tricked by North Korean agents.
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