Selangor Police chief Datuk Abdul Samah Mat said the 26-year-old man is believed to be the boyfriend of an Indonesian woman suspect who was arrested early Thursday.
The man was held to help trace the Indonesian woman. She was arrested early today," he said.
Inspector-General of Police Tan Sri Khalid Abu Bakar, in a statement, said a woman who went by the name of Siti Aishah and born in Serang, Indonesia, on 11 Feb 1992, had been arrested. She held an Indonesian passport.
Siti Aishah is the second woman to have been arrested over the killing.
The first woman, identified as Doan Thi Huong, 29, bearer of a Vietnamese passport, was arrested at KL International Airport 2 (klia2) at 8.20am on Wednesday.
"She was identified based on CCTV footage at the airport and was alone at the time of arrest, " he said.
Last Monday, Jong-Nam was reportedly at klia2 at 8am to board a flight to Macau an hour later when a woman suddenly covered his face with a cloth laced with poison.
Jong-Nam, who had used the name Kim Chol, reportedly died on the way to the Putrajaya Hospital.
More arrests were expected. It was learnt that police are seeking four men to assist the investigation.
Indonesia's Foreign Ministry said the embassy has requested consular access to provide assistance in order to ensure her legal rights," the statement said.
Investigators in Malaysia are trying to shed light on the death of Kim, which has set off set off waves of speculation over whether North Korea dispatched a hit squad to kill him.