Authorities are still waiting for the results of the post-mortem examination of Mr Kim's body, and are seeking his family members to provide a DNA sample.
Named by the police chief as suspects are Hyon Kwang Song, 44, second secretary at the embassy, who arrived in Malaysia on Sept 20, 2016, and Kim Uk Il, 37, who is employed by the country's national carrier, Air Koryo.
"We hope that the Korean embassy will cooperate with us, allow us to interview them and interview them quickly", Khalid said, adding, "If not, we will compel them to come to us".
They are now seeking four more North Korean men, who entered the country on different dates in the fortnight running up to the assassination, and all left on the day it was carried out.
Four are thought to have fled Malaysia the day Kim died and returned to Pyongyang, while another three remain at large in Malaysia, police said.
CCTV footage, reportedly from the airport, appears to show a woman approach Mr Kim from behind before wiping fast-acting poison on his face.
Khalid said the women knew they were handling poisonous materials and "were warned to take precautions". "It will be done in a professional manner, up to global standards and I don't think any country should cast any doubts on our capacity to be professional".
"So she knew very well that it is toxic and she has to wash her hands", he said.
In the days following the attack, police announced they had arrested a 28-year-old Vietnamese woman called Doan Thi Huong, as well as 25-year-old Indonesian Siti Aishah and her Malaysian boyfriend.
The Indonesian woman has told investigators that she was duped into thinking she was part of a comedy show prank.
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The Malaysian foreign ministry said the government has kept the North Korean Embassy informed, telling them that because "the death occurred in Malaysian soil under mysterious circumstances, it is the responsibility of the Malaysian government to conduct an investigation to identify the cause of death".
Police have already arrested four people in connection with the attack, including the two women. Kim Jong Nam was not known to be seeking political power; he was best known for his penchants for drinking, gambling and expensive restaurants.
The autopsy showed no evidence of a heart attack in Kim Jong Nam's death, or sign of puncture wounds on his body, Noor Hisham Abdullah, the director general of health, told reporters. He added that Malaysian authorities had received no help so far from North Korea.
The agency quoted a Seoul government source as saying Kim Jong-Nam was killed on Monday.
The incident has sparked a diplomatic spat between the two countries, with North Korea earlier this week slamming Malaysia for colluding with South Korea to defame its image, as well as Pyongyang's envoy to Malaysia being recalled.
Kim Jong-nam, the estranged half-brother of North Korea's leader, Kim Jong-un, had been living in exile in Macau with his family for several years.
"How is it possible that these female suspects could be alive after the incident?" it said in the statement.
Last year, the chief executive of the Malaysia External Trade Development Corp, Dzulkifli Mahmud, spoke of North Korea "using Malaysia as a gateway to Southeast Asian markets as it finds the country business-friendly with pro-business policies".
In 2011, a North Korean agent was arrested by the South Korean authorities for attempting to assassinate defector cum social activist Park Sang-Ha, also with a poisoned needle.